> For the complete documentation index, see [llms.txt](https://docs.idlayr.com/llms.txt). Markdown versions of documentation pages are available by appending `.md` to page URLs; this page is available as [Markdown](https://docs.idlayr.com/api-reference/reverse-sms/v1.md).
# v1
Mobile-originated SMS verification. Create a Check, have the end-user text the supplied `expected_sms_body` to the `receiver_phone_number`, and the platform resolves whether the phone number is verified.
## List Checks
> Get a page of Checks scoped to the calling project.
```json
{"openapi":"3.1.0","info":{"title":"IDlayr Reverse SMS API","version":"1.0.0"},"tags":[{"name":"reverse_sms_check_v1","description":"Mobile-originated SMS verification. Create a Check, have the end-user text the supplied\n`expected_sms_body` to the `receiver_phone_number`, and the platform resolves whether the phone number is\nverified.\n"}],"servers":[{"url":"https://{data_residency}.api.idlayr.com","description":"For accounts with data residency in the EU or US.","variables":{"data_residency":{"default":"eu","enum":["eu","us"]}}}],"security":[{"ProjectBearerAuth":["reverse_sms"]}],"components":{"securitySchemes":{"ProjectBearerAuth":{"description":"The IDlayr APIs expect the bearer token to be an\n[OAuth2 Access Token](https://tools.ietf.org/html/rfc6749#section-1.4), minted via the\nclient-credentials grant against the token endpoint. The token must carry the\n`reverse_sms` scope to call the Reverse SMS API.\n\nThe token should be presented in the `Authorization` HTTP header, e.g.\n`Authorization: Bearer {access_token}`. See\n[Create an Access Token](/docs/reference/basics#operation/oauth2-token).\n\nThe token must be associated with an IDlayr Project — minted using the Project's\n`client_id` and `client_secret`.\n","type":"oauth2","flows":{"clientCredentials":{"tokenUrl":"https://eu.api.idlayr.com/oauth2/token","scopes":{"reverse_sms":"Reverse SMS verification"}}}}},"parameters":{"pageSize":{"name":"size","description":"The number of items returned per page.","in":"query","schema":{"type":"integer","default":10,"minimum":1,"maximum":100}},"pageNumber":{"name":"page","description":"The page number being requested.","in":"query","schema":{"type":"integer","default":1,"minimum":1}}},"headers":{"X-RateLimit-Limit":{"description":"Request limit per second.","schema":{"type":"integer"},"required":true},"X-RateLimit-Remaining":{"description":"Remaining requests for the rate limit period.","schema":{"type":"integer"},"required":true},"X-RateLimit-Reset":{"description":"Time left, in seconds, for `X-RateLimit-Remaining` to be reset.","schema":{"type":"integer"},"required":true}},"schemas":{"ReverseSmsCheckPage":{"description":"Page wrapper for a list of Checks: a `content` array plus a `page` block\nwith `size` / `number` / `total_pages` / `total_elements` metadata.\n","type":"object","unevaluatedProperties":false,"required":["content","page"],"properties":{"content":{"description":"Checks in the current page.","type":"array","items":{"$ref":"#/components/schemas/ReverseSmsCheck"}},"page":{"description":"Pagination metadata for the collection.","$ref":"#/components/schemas/page"}}},"ReverseSmsCheck":{"description":"A Check resource. Which optional fields are present depends on `status`:\n- `ACCEPTED` (create response): `receiver_phone_number`, `expected_sms_body` and `ttl` are present; the end-user\n texts `expected_sms_body` to `receiver_phone_number`. These three values are returned\n **only** on the create response and are not echoed back on subsequent reads — your\n backend must persist them.\n- `PENDING`: in-flight; `receiver_phone_number`/`expected_sms_body`/`ttl` are not echoed back on reads.\n- `COMPLETED`: `match` reflects the verification result.\n- `ERROR`: `error_code` carries the reason.\n- `EXPIRED`: terminal state; the TTL elapsed before the mobile-originated SMS was received. No `error_code`.\n","type":"object","unevaluatedProperties":false,"required":["check_id","status","created_at"],"properties":{"check_id":{"description":"The unique ID of the Check resource.","$ref":"#/components/schemas/UUID"},"status":{"$ref":"#/components/schemas/ReverseSmsCheckStatus"},"receiver_phone_number":{"description":"The destination number the end-user must text, in E.164 format. Present on the create\nresponse (`ACCEPTED`).\n","type":"string","format":"E.164"},"expected_sms_body":{"description":"The exact SMS body the end-user must send, including the one-time verification code.\nPresent on the create response (`ACCEPTED`).\n","type":"string"},"match":{"description":"Whether the source MSISDN of the mobile-originated SMS matched the claimed\nphone number. Present when `status` is `COMPLETED`.\n","type":"boolean"},"ttl":{"description":"Time-to-live, in seconds, before the Check transitions to `EXPIRED`. Present on the create response.","type":"integer"},"created_at":{"description":"When the Check was created.","$ref":"#/components/schemas/ISODateTime"},"updated_at":{"description":"When the Check was last updated.","$ref":"#/components/schemas/ISODateTime"},"reference_id":{"description":"Caller-supplied reference, echoed from the create request.","type":"string","maxLength":50},"error_code":{"description":"Machine-readable error code. Set when `status` is `ERROR`.","$ref":"#/components/schemas/ReverseSmsCheckErrorCode"}}},"UUID":{"description":"A Universally Unique IDentifier.","type":"string","format":"uuid","pattern":"[0-9a-f]{8}-[0-9a-f]{4}-[0-9a-f]{4}-[0-9a-f]{4}-[0-9a-f]{12}"},"ReverseSmsCheckStatus":{"description":"The status of a Check:\n- `ACCEPTED`: The Check has been authorized; the platform is awaiting the mobile-originated SMS.\n- `PENDING`: The Check is in-flight, awaiting the mobile-originated SMS.\n- `COMPLETED`: The Check has completed and `match` reflects the result.\n- `EXPIRED`: The Check expired before the mobile-originated SMS was received.\n- `ERROR`: An error prevented the Check from completing; see `error_code`.\n","type":"string","enum":["ACCEPTED","PENDING","COMPLETED","EXPIRED","ERROR"]},"ISODateTime":{"description":"A DateTime conforming to ISO 8601 specifications.","type":"string","format":"date-time"},"ReverseSmsCheckErrorCode":{"description":"Machine-readable error code carried on `ERROR`-status Checks.\n\nThe full Reverse SMS error catalogue (including request-level 4xx codes and\nterminal-state codes) is published at\n[docs.idlayr.com/products/number-verification/reverse-sms/error-codes](https://docs.idlayr.com/products/number-verification/reverse-sms/error-codes).\nThe terminal-state catalogue is still being finalised — this enum will grow\nadditively as new codes land in the docs.\n\n- `internal_error`: an unexpected internal failure.\n","type":"string","enum":["internal_error"]},"page":{"description":"Pagination metadata.","type":"object","unevaluatedProperties":false,"required":["size","number","total_pages","total_elements"],"properties":{"size":{"description":"The number of records per page.","type":"integer"},"number":{"description":"The current page number.","type":"integer"},"total_pages":{"description":"The total number of pages available.","type":"integer"},"total_elements":{"description":"The total number of records across all pages.","type":"integer"}}},"RsqlBadRequest":{"description":"The `search` query parameter is not a syntactically valid\n[RSQL](https://github.com/jirutka/rsql-parser) expression, or references a field that\nis not filterable on this resource.\n","type":"object","unevaluatedProperties":false,"required":["type","title","status","detail","error_code"],"properties":{"type":{"description":"A URI reference [RFC 3986] that identifies the problem type.","type":"string"},"title":{"description":"A short, human-readable summary of the problem type.","type":"string"},"status":{"description":"The HTTP status code generated by the origin server for this occurrence of the problem.","type":"integer"},"detail":{"description":"A human-readable explanation specific to this occurrence of the problem.","type":"string"},"error_code":{"description":"Machine-readable error code identifying the problem type.","type":"string"}}},"Unauthenticated":{"description":"The request lacks a valid Access Token, or the token has expired. Mint a new token via\nthe OAuth2 token endpoint and retry.\n","type":"object","unevaluatedProperties":false,"required":["type","title","status","detail","error_code"],"properties":{"type":{"description":"A URI reference [RFC 3986] that identifies the problem type.","type":"string"},"title":{"description":"A short, human-readable summary of the problem type.","type":"string"},"status":{"description":"The HTTP status code generated by the origin server for this occurrence of the problem.","type":"integer"},"detail":{"description":"A human-readable explanation specific to this occurrence of the problem.","type":"string"},"error_code":{"description":"Machine-readable error code identifying the problem type.","type":"string"}}},"Forbidden":{"description":"The Access Token is valid but does not grant access to the requested resource. Common\ncauses: the token does not carry the required product scope, the token's Project is\nnot enabled for this product, or the resource belongs to a different Project.\n","type":"object","unevaluatedProperties":false,"required":["type","title","status","detail","error_code"],"properties":{"type":{"description":"A URI reference [RFC 3986] that identifies the problem type.","type":"string"},"title":{"description":"A short, human-readable summary of the problem type.","type":"string"},"status":{"description":"The HTTP status code generated by the origin server for this occurrence of the problem.","type":"integer"},"detail":{"description":"A human-readable explanation specific to this occurrence of the problem.","type":"string"},"error_code":{"description":"Machine-readable error code identifying the problem type.","type":"string"}}},"RateLimitReached":{"description":"The API rate limit for the workspace has been exceeded. The `Retry-After` header carries\nthe number of seconds after which the caller can retry.\n","type":"object","unevaluatedProperties":false,"required":["type","title","status","detail","error_code"],"properties":{"type":{"description":"A URI reference [RFC 3986] that identifies the problem type.","type":"string"},"title":{"description":"A short, human-readable summary of the problem type.","type":"string"},"status":{"description":"The HTTP status code generated by the origin server for this occurrence of the problem.","type":"integer"},"detail":{"description":"A human-readable explanation specific to this occurrence of the problem.","type":"string"},"error_code":{"description":"Machine-readable error code identifying the problem type.","type":"string"}}}}},"paths":{"/v1/number-verification/reverse-sms-checks":{"get":{"summary":"List Checks","description":"Get a page of Checks scoped to the calling project.","operationId":"get-reverse-sms-checks-v1","tags":["reverse_sms_check_v1"],"parameters":[{"$ref":"#/components/parameters/pageSize"},{"$ref":"#/components/parameters/pageNumber"},{"name":"search","in":"query","description":"Optional RSQL filter applied on top of the implicit project scope. Filterable fields: status, verified, network_id, error_code, reference_id, created_at, updated_at.","required":false,"schema":{"type":"string"}}],"responses":{"200":{"description":"A page of Checks.","headers":{"X-RateLimit-Limit":{"$ref":"#/components/headers/X-RateLimit-Limit"},"X-RateLimit-Remaining":{"$ref":"#/components/headers/X-RateLimit-Remaining"},"X-RateLimit-Reset":{"$ref":"#/components/headers/X-RateLimit-Reset"}},"content":{"application/json":{"schema":{"$ref":"#/components/schemas/ReverseSmsCheckPage"}}}},"400":{"description":"Bad Request","content":{"application/problem+json":{"schema":{"$ref":"#/components/schemas/RsqlBadRequest"}}}},"401":{"description":"Unauthenticated","content":{"application/problem+json":{"schema":{"$ref":"#/components/schemas/Unauthenticated"}}}},"403":{"description":"Forbidden","content":{"application/problem+json":{"schema":{"$ref":"#/components/schemas/Forbidden"}}}},"429":{"description":"Rate Limit Reached","content":{"application/problem+json":{"schema":{"$ref":"#/components/schemas/RateLimitReached"}}}}}}}}}
```
## Create a Check
> Starts a Reverse SMS verification flow. The response includes the Check \`status\`\
> (initially \`ACCEPTED\`), the \`receiver\_phone\_number\` to text, and the \`expected\_sms\_body\` to send.
```json
{"openapi":"3.1.0","info":{"title":"IDlayr Reverse SMS API","version":"1.0.0"},"tags":[{"name":"reverse_sms_check_v1","description":"Mobile-originated SMS verification. Create a Check, have the end-user text the supplied\n`expected_sms_body` to the `receiver_phone_number`, and the platform resolves whether the phone number is\nverified.\n"}],"servers":[{"url":"https://{data_residency}.api.idlayr.com","description":"For accounts with data residency in the EU or US.","variables":{"data_residency":{"default":"eu","enum":["eu","us"]}}}],"security":[{"ProjectBearerAuth":["reverse_sms"]}],"components":{"securitySchemes":{"ProjectBearerAuth":{"description":"The IDlayr APIs expect the bearer token to be an\n[OAuth2 Access Token](https://tools.ietf.org/html/rfc6749#section-1.4), minted via the\nclient-credentials grant against the token endpoint. The token must carry the\n`reverse_sms` scope to call the Reverse SMS API.\n\nThe token should be presented in the `Authorization` HTTP header, e.g.\n`Authorization: Bearer {access_token}`. See\n[Create an Access Token](/docs/reference/basics#operation/oauth2-token).\n\nThe token must be associated with an IDlayr Project — minted using the Project's\n`client_id` and `client_secret`.\n","type":"oauth2","flows":{"clientCredentials":{"tokenUrl":"https://eu.api.idlayr.com/oauth2/token","scopes":{"reverse_sms":"Reverse SMS verification"}}}}},"schemas":{"ReverseSmsCheckCreatePayload":{"description":"Payload for creating a Check.","type":"object","unevaluatedProperties":false,"required":["phone_number"],"properties":{"phone_number":{"description":"The phone number to verify, in [E.164 format](https://www.itu.int/rec/T-REC-E.164-201011-I/en) (leading `+`).","type":"string","format":"E.164"},"reference_id":{"description":"Optional. Your own internal reference for this Check; echoed back on responses and webhooks.\nDo not use Personally Identifiable Information (PII).\n","type":"string","maxLength":50},"callback_url":{"description":"Optional. URL the platform will POST the webhook payload to when the Check reaches a terminal status.","type":"string","format":"uri"}}},"ReverseSmsCheckCallbackPayload":{"description":"Body POSTed to the customer-supplied `callback_url` when the Check reaches a terminal\nstatus. `status` is one of `COMPLETED`, `ERROR`, or `EXPIRED`.\n","type":"object","unevaluatedProperties":false,"required":["check_id","status","created_at"],"properties":{"check_id":{"description":"The unique ID of the Check resource.","$ref":"#/components/schemas/UUID"},"status":{"description":"Terminal status. Callbacks are not fired for `ACCEPTED` or `PENDING`.","type":"string","enum":["COMPLETED","ERROR","EXPIRED"]},"match":{"description":"Whether the source MSISDN of the mobile-originated SMS matched the claimed\nphone number. Present when `status` is `COMPLETED`.\n","type":"boolean"},"created_at":{"description":"When the Check was created.","$ref":"#/components/schemas/ISODateTime"},"updated_at":{"description":"When the Check was last updated.","$ref":"#/components/schemas/ISODateTime"},"reference_id":{"description":"Caller-supplied reference, echoed from the create request.","type":"string","maxLength":50},"error_code":{"description":"Machine-readable error code. Set when `status` is `ERROR`.","$ref":"#/components/schemas/ReverseSmsCheckErrorCode"}}},"UUID":{"description":"A Universally Unique IDentifier.","type":"string","format":"uuid","pattern":"[0-9a-f]{8}-[0-9a-f]{4}-[0-9a-f]{4}-[0-9a-f]{4}-[0-9a-f]{12}"},"ISODateTime":{"description":"A DateTime conforming to ISO 8601 specifications.","type":"string","format":"date-time"},"ReverseSmsCheckErrorCode":{"description":"Machine-readable error code carried on `ERROR`-status Checks.\n\nThe full Reverse SMS error catalogue (including request-level 4xx codes and\nterminal-state codes) is published at\n[docs.idlayr.com/products/number-verification/reverse-sms/error-codes](https://docs.idlayr.com/products/number-verification/reverse-sms/error-codes).\nThe terminal-state catalogue is still being finalised — this enum will grow\nadditively as new codes land in the docs.\n\n- `internal_error`: an unexpected internal failure.\n","type":"string","enum":["internal_error"]},"ReverseSmsCheck":{"description":"A Check resource. Which optional fields are present depends on `status`:\n- `ACCEPTED` (create response): `receiver_phone_number`, `expected_sms_body` and `ttl` are present; the end-user\n texts `expected_sms_body` to `receiver_phone_number`. These three values are returned\n **only** on the create response and are not echoed back on subsequent reads — your\n backend must persist them.\n- `PENDING`: in-flight; `receiver_phone_number`/`expected_sms_body`/`ttl` are not echoed back on reads.\n- `COMPLETED`: `match` reflects the verification result.\n- `ERROR`: `error_code` carries the reason.\n- `EXPIRED`: terminal state; the TTL elapsed before the mobile-originated SMS was received. No `error_code`.\n","type":"object","unevaluatedProperties":false,"required":["check_id","status","created_at"],"properties":{"check_id":{"description":"The unique ID of the Check resource.","$ref":"#/components/schemas/UUID"},"status":{"$ref":"#/components/schemas/ReverseSmsCheckStatus"},"receiver_phone_number":{"description":"The destination number the end-user must text, in E.164 format. Present on the create\nresponse (`ACCEPTED`).\n","type":"string","format":"E.164"},"expected_sms_body":{"description":"The exact SMS body the end-user must send, including the one-time verification code.\nPresent on the create response (`ACCEPTED`).\n","type":"string"},"match":{"description":"Whether the source MSISDN of the mobile-originated SMS matched the claimed\nphone number. Present when `status` is `COMPLETED`.\n","type":"boolean"},"ttl":{"description":"Time-to-live, in seconds, before the Check transitions to `EXPIRED`. Present on the create response.","type":"integer"},"created_at":{"description":"When the Check was created.","$ref":"#/components/schemas/ISODateTime"},"updated_at":{"description":"When the Check was last updated.","$ref":"#/components/schemas/ISODateTime"},"reference_id":{"description":"Caller-supplied reference, echoed from the create request.","type":"string","maxLength":50},"error_code":{"description":"Machine-readable error code. Set when `status` is `ERROR`.","$ref":"#/components/schemas/ReverseSmsCheckErrorCode"}}},"ReverseSmsCheckStatus":{"description":"The status of a Check:\n- `ACCEPTED`: The Check has been authorized; the platform is awaiting the mobile-originated SMS.\n- `PENDING`: The Check is in-flight, awaiting the mobile-originated SMS.\n- `COMPLETED`: The Check has completed and `match` reflects the result.\n- `EXPIRED`: The Check expired before the mobile-originated SMS was received.\n- `ERROR`: An error prevented the Check from completing; see `error_code`.\n","type":"string","enum":["ACCEPTED","PENDING","COMPLETED","EXPIRED","ERROR"]},"PhoneNumberBadRequest":{"description":"The request could not be processed for the supplied phone number. `error_code`\ndistinguishes the cause:\n- `phone_number_invalid`: the supplied phone number is not valid E.164.\n- `mno_not_supported`: the Mobile Network Operator for the supplied number is not supported.\n","type":"object","unevaluatedProperties":false,"required":["type","title","status","detail","error_code"],"properties":{"type":{"description":"A URI reference [RFC 3986] that identifies the problem type.","type":"string"},"title":{"description":"A short, human-readable summary of the problem type.","type":"string"},"status":{"description":"The HTTP status code generated by the origin server for this occurrence of the problem.","type":"integer"},"detail":{"description":"A human-readable explanation specific to this occurrence of the problem.","type":"string"},"error_code":{"description":"Machine-readable error code identifying the cause of the bad request.","type":"string","enum":["phone_number_invalid","mno_not_supported"]}}},"Unauthenticated":{"description":"The request lacks a valid Access Token, or the token has expired. Mint a new token via\nthe OAuth2 token endpoint and retry.\n","type":"object","unevaluatedProperties":false,"required":["type","title","status","detail","error_code"],"properties":{"type":{"description":"A URI reference [RFC 3986] that identifies the problem type.","type":"string"},"title":{"description":"A short, human-readable summary of the problem type.","type":"string"},"status":{"description":"The HTTP status code generated by the origin server for this occurrence of the problem.","type":"integer"},"detail":{"description":"A human-readable explanation specific to this occurrence of the problem.","type":"string"},"error_code":{"description":"Machine-readable error code identifying the problem type.","type":"string"}}},"Forbidden":{"description":"The Access Token is valid but does not grant access to the requested resource. Common\ncauses: the token does not carry the required product scope, the token's Project is\nnot enabled for this product, or the resource belongs to a different Project.\n","type":"object","unevaluatedProperties":false,"required":["type","title","status","detail","error_code"],"properties":{"type":{"description":"A URI reference [RFC 3986] that identifies the problem type.","type":"string"},"title":{"description":"A short, human-readable summary of the problem type.","type":"string"},"status":{"description":"The HTTP status code generated by the origin server for this occurrence of the problem.","type":"integer"},"detail":{"description":"A human-readable explanation specific to this occurrence of the problem.","type":"string"},"error_code":{"description":"Machine-readable error code identifying the problem type.","type":"string"}}},"RateLimitReached":{"description":"The API rate limit for the workspace has been exceeded. The `Retry-After` header carries\nthe number of seconds after which the caller can retry.\n","type":"object","unevaluatedProperties":false,"required":["type","title","status","detail","error_code"],"properties":{"type":{"description":"A URI reference [RFC 3986] that identifies the problem type.","type":"string"},"title":{"description":"A short, human-readable summary of the problem type.","type":"string"},"status":{"description":"The HTTP status code generated by the origin server for this occurrence of the problem.","type":"integer"},"detail":{"description":"A human-readable explanation specific to this occurrence of the problem.","type":"string"},"error_code":{"description":"Machine-readable error code identifying the problem type.","type":"string"}}}},"parameters":{"digest":{"name":"digest","in":"header","description":"The body contents hashed with the algorithm identified in the `Authorization` header\nand then Base64 encoded (e.g. `SHA-256=base64(SHA256(body))`).\n","schema":{"type":"string"}},"date":{"name":"date","in":"header","description":"The date and time at which the message was originated.","schema":{"type":"string"}},"host":{"name":"host","in":"header","description":"The host and port number of the server to which the request is being sent.","schema":{"type":"string"}}},"headers":{"X-RateLimit-Limit":{"description":"Request limit per second.","schema":{"type":"integer"},"required":true},"X-RateLimit-Remaining":{"description":"Remaining requests for the rate limit period.","schema":{"type":"integer"},"required":true},"X-RateLimit-Reset":{"description":"Time left, in seconds, for `X-RateLimit-Remaining` to be reset.","schema":{"type":"integer"},"required":true}}},"paths":{"/v1/number-verification/reverse-sms-checks":{"post":{"summary":"Create a Check","description":"Starts a Reverse SMS verification flow. The response includes the Check `status`\n(initially `ACCEPTED`), the `receiver_phone_number` to text, and the `expected_sms_body` to send.\n","operationId":"create-reverse-sms-check-v1","tags":["reverse_sms_check_v1"],"requestBody":{"description":"JSON payload to create a Check.","required":true,"content":{"application/json":{"schema":{"$ref":"#/components/schemas/ReverseSmsCheckCreatePayload"}}}},"callbacks":{"reverseSmsCheckEndStatus":{"{$request.body#/callback_url}":{"post":{"summary":"Check has reached a terminal status","description":"Sent once when the Check transitions to a terminal status (`COMPLETED`,\n`EXPIRED`, or `ERROR`).\n","parameters":[{"name":"x-idlayr-callback","in":"header","description":"Identifies the webhook source. Value is `reverse_sms`.","required":true,"schema":{"type":"string","enum":["reverse_sms"]}},{"name":"Authorization","in":"header","description":"HTTP message signature. Format:\n`Signature keyId=\"\",algorithm=\"rsa-sha256\",headers=\"(request-target) host date x-idlayr-callback digest\",signature=\"\"`.\n\n- `keyId` identifies the public key (fetch from the IDlayr JWKS endpoint).\n- `algorithm` is `rsa-sha256`.\n- `headers` lists the canonical components included in the signature\n input: `(request-target)`, `host`, `date`, `x-idlayr-callback`,\n `digest`.\n- `signature` is the base64-encoded RSA-SHA256 signature.\n\nSee [Signed HTTP Messages](/docs/authentication#signed).\n","required":true,"schema":{"type":"string"}},{"$ref":"#/components/parameters/digest"},{"$ref":"#/components/parameters/date"},{"$ref":"#/components/parameters/host"}],"requestBody":{"required":true,"content":{"application/json":{"schema":{"$ref":"#/components/schemas/ReverseSmsCheckCallbackPayload"}}}},"responses":{"200":{"description":"The receiving server should return a 200 response to indicate it has\nprocessed the callback. Upon receipt of a non-200 response a retry process\nwill begin (1 immediate attempt + up to 6 retries at 10/20/30/40/50/60s\ngaps, ~3.5 min total).\n"}}}}}},"responses":{"201":{"description":"Check created.","headers":{"X-RateLimit-Limit":{"$ref":"#/components/headers/X-RateLimit-Limit"},"X-RateLimit-Remaining":{"$ref":"#/components/headers/X-RateLimit-Remaining"},"X-RateLimit-Reset":{"$ref":"#/components/headers/X-RateLimit-Reset"}},"content":{"application/json":{"schema":{"$ref":"#/components/schemas/ReverseSmsCheck"}}}},"400":{"description":"Bad Request","content":{"application/problem+json":{"schema":{"$ref":"#/components/schemas/PhoneNumberBadRequest"}}}},"401":{"description":"Unauthenticated","content":{"application/problem+json":{"schema":{"$ref":"#/components/schemas/Unauthenticated"}}}},"403":{"description":"Forbidden","content":{"application/problem+json":{"schema":{"$ref":"#/components/schemas/Forbidden"}}}},"429":{"description":"Rate Limit Reached","content":{"application/problem+json":{"schema":{"$ref":"#/components/schemas/RateLimitReached"}}}}}}}}}
```
## Get a Check
> Get the Check identified by \`check\_id\`.
```json
{"openapi":"3.1.0","info":{"title":"IDlayr Reverse SMS API","version":"1.0.0"},"tags":[{"name":"reverse_sms_check_v1","description":"Mobile-originated SMS verification. Create a Check, have the end-user text the supplied\n`expected_sms_body` to the `receiver_phone_number`, and the platform resolves whether the phone number is\nverified.\n"}],"servers":[{"url":"https://{data_residency}.api.idlayr.com","description":"For accounts with data residency in the EU or US.","variables":{"data_residency":{"default":"eu","enum":["eu","us"]}}}],"security":[{"ProjectBearerAuth":["reverse_sms"]}],"components":{"securitySchemes":{"ProjectBearerAuth":{"description":"The IDlayr APIs expect the bearer token to be an\n[OAuth2 Access Token](https://tools.ietf.org/html/rfc6749#section-1.4), minted via the\nclient-credentials grant against the token endpoint. The token must carry the\n`reverse_sms` scope to call the Reverse SMS API.\n\nThe token should be presented in the `Authorization` HTTP header, e.g.\n`Authorization: Bearer {access_token}`. See\n[Create an Access Token](/docs/reference/basics#operation/oauth2-token).\n\nThe token must be associated with an IDlayr Project — minted using the Project's\n`client_id` and `client_secret`.\n","type":"oauth2","flows":{"clientCredentials":{"tokenUrl":"https://eu.api.idlayr.com/oauth2/token","scopes":{"reverse_sms":"Reverse SMS verification"}}}}},"headers":{"X-RateLimit-Limit":{"description":"Request limit per second.","schema":{"type":"integer"},"required":true},"X-RateLimit-Remaining":{"description":"Remaining requests for the rate limit period.","schema":{"type":"integer"},"required":true},"X-RateLimit-Reset":{"description":"Time left, in seconds, for `X-RateLimit-Remaining` to be reset.","schema":{"type":"integer"},"required":true}},"schemas":{"ReverseSmsCheck":{"description":"A Check resource. Which optional fields are present depends on `status`:\n- `ACCEPTED` (create response): `receiver_phone_number`, `expected_sms_body` and `ttl` are present; the end-user\n texts `expected_sms_body` to `receiver_phone_number`. These three values are returned\n **only** on the create response and are not echoed back on subsequent reads — your\n backend must persist them.\n- `PENDING`: in-flight; `receiver_phone_number`/`expected_sms_body`/`ttl` are not echoed back on reads.\n- `COMPLETED`: `match` reflects the verification result.\n- `ERROR`: `error_code` carries the reason.\n- `EXPIRED`: terminal state; the TTL elapsed before the mobile-originated SMS was received. No `error_code`.\n","type":"object","unevaluatedProperties":false,"required":["check_id","status","created_at"],"properties":{"check_id":{"description":"The unique ID of the Check resource.","$ref":"#/components/schemas/UUID"},"status":{"$ref":"#/components/schemas/ReverseSmsCheckStatus"},"receiver_phone_number":{"description":"The destination number the end-user must text, in E.164 format. Present on the create\nresponse (`ACCEPTED`).\n","type":"string","format":"E.164"},"expected_sms_body":{"description":"The exact SMS body the end-user must send, including the one-time verification code.\nPresent on the create response (`ACCEPTED`).\n","type":"string"},"match":{"description":"Whether the source MSISDN of the mobile-originated SMS matched the claimed\nphone number. Present when `status` is `COMPLETED`.\n","type":"boolean"},"ttl":{"description":"Time-to-live, in seconds, before the Check transitions to `EXPIRED`. Present on the create response.","type":"integer"},"created_at":{"description":"When the Check was created.","$ref":"#/components/schemas/ISODateTime"},"updated_at":{"description":"When the Check was last updated.","$ref":"#/components/schemas/ISODateTime"},"reference_id":{"description":"Caller-supplied reference, echoed from the create request.","type":"string","maxLength":50},"error_code":{"description":"Machine-readable error code. Set when `status` is `ERROR`.","$ref":"#/components/schemas/ReverseSmsCheckErrorCode"}}},"UUID":{"description":"A Universally Unique IDentifier.","type":"string","format":"uuid","pattern":"[0-9a-f]{8}-[0-9a-f]{4}-[0-9a-f]{4}-[0-9a-f]{4}-[0-9a-f]{12}"},"ReverseSmsCheckStatus":{"description":"The status of a Check:\n- `ACCEPTED`: The Check has been authorized; the platform is awaiting the mobile-originated SMS.\n- `PENDING`: The Check is in-flight, awaiting the mobile-originated SMS.\n- `COMPLETED`: The Check has completed and `match` reflects the result.\n- `EXPIRED`: The Check expired before the mobile-originated SMS was received.\n- `ERROR`: An error prevented the Check from completing; see `error_code`.\n","type":"string","enum":["ACCEPTED","PENDING","COMPLETED","EXPIRED","ERROR"]},"ISODateTime":{"description":"A DateTime conforming to ISO 8601 specifications.","type":"string","format":"date-time"},"ReverseSmsCheckErrorCode":{"description":"Machine-readable error code carried on `ERROR`-status Checks.\n\nThe full Reverse SMS error catalogue (including request-level 4xx codes and\nterminal-state codes) is published at\n[docs.idlayr.com/products/number-verification/reverse-sms/error-codes](https://docs.idlayr.com/products/number-verification/reverse-sms/error-codes).\nThe terminal-state catalogue is still being finalised — this enum will grow\nadditively as new codes land in the docs.\n\n- `internal_error`: an unexpected internal failure.\n","type":"string","enum":["internal_error"]},"Unauthenticated":{"description":"The request lacks a valid Access Token, or the token has expired. Mint a new token via\nthe OAuth2 token endpoint and retry.\n","type":"object","unevaluatedProperties":false,"required":["type","title","status","detail","error_code"],"properties":{"type":{"description":"A URI reference [RFC 3986] that identifies the problem type.","type":"string"},"title":{"description":"A short, human-readable summary of the problem type.","type":"string"},"status":{"description":"The HTTP status code generated by the origin server for this occurrence of the problem.","type":"integer"},"detail":{"description":"A human-readable explanation specific to this occurrence of the problem.","type":"string"},"error_code":{"description":"Machine-readable error code identifying the problem type.","type":"string"}}},"Forbidden":{"description":"The Access Token is valid but does not grant access to the requested resource. Common\ncauses: the token does not carry the required product scope, the token's Project is\nnot enabled for this product, or the resource belongs to a different Project.\n","type":"object","unevaluatedProperties":false,"required":["type","title","status","detail","error_code"],"properties":{"type":{"description":"A URI reference [RFC 3986] that identifies the problem type.","type":"string"},"title":{"description":"A short, human-readable summary of the problem type.","type":"string"},"status":{"description":"The HTTP status code generated by the origin server for this occurrence of the problem.","type":"integer"},"detail":{"description":"A human-readable explanation specific to this occurrence of the problem.","type":"string"},"error_code":{"description":"Machine-readable error code identifying the problem type.","type":"string"}}},"CheckNotFound":{"description":"The Check identified by `check_id` does not exist or is no longer retrievable.","type":"object","unevaluatedProperties":false,"required":["type","title","status","detail","error_code"],"properties":{"type":{"description":"A URI reference [RFC 3986] that identifies the problem type.","type":"string"},"title":{"description":"A short, human-readable summary of the problem type.","type":"string"},"status":{"description":"The HTTP status code generated by the origin server for this occurrence of the problem.","type":"integer"},"detail":{"description":"A human-readable explanation specific to this occurrence of the problem.","type":"string"},"error_code":{"description":"Machine-readable error code identifying the problem type.","type":"string"}}},"RateLimitReached":{"description":"The API rate limit for the workspace has been exceeded. The `Retry-After` header carries\nthe number of seconds after which the caller can retry.\n","type":"object","unevaluatedProperties":false,"required":["type","title","status","detail","error_code"],"properties":{"type":{"description":"A URI reference [RFC 3986] that identifies the problem type.","type":"string"},"title":{"description":"A short, human-readable summary of the problem type.","type":"string"},"status":{"description":"The HTTP status code generated by the origin server for this occurrence of the problem.","type":"integer"},"detail":{"description":"A human-readable explanation specific to this occurrence of the problem.","type":"string"},"error_code":{"description":"Machine-readable error code identifying the problem type.","type":"string"}}}}},"paths":{"/v1/number-verification/reverse-sms-checks/{check_id}":{"get":{"summary":"Get a Check","description":"Get the Check identified by `check_id`.","operationId":"get-reverse-sms-check-v1","tags":["reverse_sms_check_v1"],"responses":{"200":{"description":"The Check.","headers":{"X-RateLimit-Limit":{"$ref":"#/components/headers/X-RateLimit-Limit"},"X-RateLimit-Remaining":{"$ref":"#/components/headers/X-RateLimit-Remaining"},"X-RateLimit-Reset":{"$ref":"#/components/headers/X-RateLimit-Reset"}},"content":{"application/json":{"schema":{"$ref":"#/components/schemas/ReverseSmsCheck"}}}},"401":{"description":"Unauthenticated","content":{"application/problem+json":{"schema":{"$ref":"#/components/schemas/Unauthenticated"}}}},"403":{"description":"Forbidden","content":{"application/problem+json":{"schema":{"$ref":"#/components/schemas/Forbidden"}}}},"404":{"description":"Check Not Found","content":{"application/problem+json":{"schema":{"$ref":"#/components/schemas/CheckNotFound"}}}},"429":{"description":"Rate Limit Reached","content":{"application/problem+json":{"schema":{"$ref":"#/components/schemas/RateLimitReached"}}}}}}}}}
```
---
# Agent Instructions
This documentation is published with GitBook. GitBook is the documentation platform designed so that both humans and AI agents can read, navigate, and reason over technical content effectively. Learn more at gitbook.com.
## Querying This Documentation
If you need additional information that is not directly available in this page, you can query the documentation dynamically by asking a question.
Perform an HTTP GET request on the current page URL with the `ask` query parameter, and the optional `goal` query parameter:
```
GET https://docs.idlayr.com/api-reference/reverse-sms/v1.md?ask=&goal=
```
`ask` is the immediate question: it should be specific, self-contained, and written in natural language.
`goal` is optional and describes the broader end goal you are ultimately trying to accomplish on behalf of the user. GitBook uses it to tailor the answer towards what is most useful for that goal.
The response will contain a direct answer to the question and relevant excerpts and sources from the documentation.
Use this mechanism when the answer is not explicitly present in the current page, you need clarification or additional context, or you want to retrieve related documentation sections.