> For the complete documentation index, see [llms.txt](https://docs.payments.thalescloud.io/llms.txt). Markdown versions of documentation pages are available by appending `.md` to page URLs; this page is available as [Markdown](https://docs.payments.thalescloud.io/classic-tokenization/get-started/api-basics/api-guidelines.md). # API guidelines ### Development considerations The following changes are considered backward compatible: * Add a new API request. * Add a new optional parameter to an existing API request or response. * Add it in the body, as a query parameter, or as an HTTP header. * Add a new enum value. * Make required parameters optional. * Ignore unknown fields or values received in an API request or response. ### Error management #### Responses and error types Responses are grouped into categories. Handle all responses in the same category the same way. The following table lists the categories and indicates: * The error types in each category. * How the issuer backend must handle these errors, including the retry policy. | CODE TYPE | CATEGORY | DESCRIPTION AND RETRY POLICY | | --------- | ---------------- | ----------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------- | | K | OK, not an error | N/A | | D | Data Error | The parameters sent by the function requester do not match with the rules checked by the function provider. | | S | System Error |

This is an unexpected error caused by a temporary failure in one or more parts of the system.
The function requester can retry the request.
Note: HTTP 5xx errors are considered system errors.

| | F | Functional Error |

This is a definitive error. Abort processing. Do not retry.
The token can no longer be used and must be deleted.

| #### Errors The table below lists the errors that can occur. Depending on the flow, an error can be returned either synchronously in the response or asynchronously in a callback. | ERROR CODE | CODE TYPE | DESCRIPTION | | ---------- | --------- | ----------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------- | | 111 | D | Missing required parameter | | 112 | D | Bad parameter format | | 113 | D | Unknown issuer | | 114 | D | Unknown end user | | 115 | D | Unknown product | | 116 | D | Unknown card | | 117 | D | Unknown token storage | | 118 | D | Unknown request | | 119 | D | Unknown virtual card | | 158 | D | Invalid parameters: card expired | | 159 | D | Invalid parameters: card suspended | | 160 | D | Invalid parameters: card revoked or deleted | | 161 | D |

Authentication value is incorrect.

| | 163 | D | Product not supported for mobile payment | | 164 | D | FPAN Provisioning Count Exceeded | | 166 | D | Invalid card information (FPAN, expiry date) or card not eligible | | 167 | D | Card already enrolled | | 168 | D | No phone number associated with the end user | | 221 | S | Device or wallet provider is not accessible after retries | | 222 | S | Device or wallet provider is busy | | 231 | F | Unexpected error from the device | | 232 | F | Insufficient memory on the device to perform the operation | | 321 | S | Operation on a token is already ongoing | | 322 | S | Operation time-to-live expired | | 323 | S | Operation partially completed (typically when an operation targets multiple virtual cards and one fails) | | 421 | S | OTP or PIN locked (retry limit exceeded) | | 422 | S | OTP expired | | 431 | F | Invalid personalization data | | 432 | F | Current token/card state does not allow this operation | | 501 | D | ID\&V method ID is invalid | | 502 | D | Communication channel is not available to send OTP | | 503 | D |

ID\&V method selected by the end user is no longer valid.
This can happen if, during enrollment, the channel data (for example, a phone number) becomes invalid for the ID\&V process.

| | 510 | F | Step-up cardholder verification declined (Visa CTF only) | | 520 | F | Step-up cardholder verification failed (Visa CTF only) | | 521 | S | Push server error | | 531 | F | Push token no longer valid | | 911 | F | Operation failed | | 920 | F | OTP generation limit exceeded | | 921 | S | Unexpected server error | --- # 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.payments.thalescloud.io/classic-tokenization/get-started/api-basics/api-guidelines.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.