> 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/products/eligibility/error-codes.md).

# Error codes

{% hint style="info" %}
**Backend API** · GA
{% endhint %}

Errors specific to Eligibility. Because Eligibility is fully synchronous, all errors are returned as HTTP responses — there are no terminal-state error codes carried in a resource body.

This page lists only Eligibility-specific codes. For the canonical, cross-product error catalogue with full semantics — see the [API Reference](https://docs.idlayr.com/api-reference).

## HTTP-response errors

<table data-header-hidden="false" data-header-sticky><thead><tr><th width="91.05859375">HTTP</th><th width="213.92578125">Error code</th><th>When</th></tr></thead><tbody><tr><td>400</td><td><code>phone_number_invalid</code></td><td>The phone number isn't in a valid international format. Use E.164 (e.g. +14155552671).</td></tr><tr><td>400</td><td>🆕 <code>invalid_ip</code></td><td>The IP address provided is missing or malformed.</td></tr><tr><td>400</td><td><code>bad_request</code></td><td>Malform request body</td></tr><tr><td>401</td><td><code>unauthorized</code></td><td>Your authentication token is missing, invalid, expired, or couldn't be verified. Get a new token and retry.</td></tr><tr><td>403</td><td><code>invalid_scope</code></td><td>Your credentials are valid but don't have permission for this endpoint or project. Request the correct scope for your token.</td></tr><tr><td>404</td><td><code>check_not_found</code></td><td>We couldn't find a check with this ID — it may be incorrect, expired, or already removed.</td></tr><tr><td>412</td><td><code>not_mobile_ip</code></td><td>This request isn't coming from a mobile data connection, which this check requires.</td></tr><tr><td>429</td><td><code>too_many_requests</code></td><td>The Project's rate limit has been exceeded.</td></tr><tr><td>500</td><td><code>internal_error</code></td><td>Something went wrong on our end. Retry, and contact support if it persists.</td></tr><tr><td>503</td><td>🆕 <code>service_unavailable</code></td><td>We're having a temporary issue on our side.</td></tr></tbody></table>

## How "no products available" differs from an error

An Eligibility response indicating that **no IDlayr products are available** for the queried number or IP is **not** an error. It's a successful response (200 OK) that happens to carry an empty product list. Your code should treat this as a normal outcome — route to the no-IDlayr fallback path — and not retry.

Errors mean IDlayr couldn't determine eligibility (bad input, no subscriber found, internal failure). "No products available" means IDlayr determined eligibility and the answer is none.


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