Errors

Protocol errors use a closed registry, 29 codes in the edition published here, and RFC 9457 Problem Details. Each registered code has one type, urn:autonym:error:<code>, one status and one title, and names the sections whose text raises it. A response carries exactly the fields type, title, status, code and request_id. Submitted values, record content, credentials, existence hints and arbitrary diagnostic details never appear in them.

The registry includes implemented operational errors, specified future recipient errors and specified refusals that reach only the person's own operations, such as the first-party sign-in and session refusals and the entry limit. It is not evidence that a recipient API or the first-party app is deployed.

OAuth authorisation and token-endpoint errors keep their own representation, and a 401 carries the WWW-Authenticate challenge. The registry lists separately the OAuth codes the specification cites and the codes the PDPP binding takes from PDPP Core; those are not registered codes. A token that fails verification at a resource fails OAuth invalid_token.

A few rules hold across every code. Revoked, expired and exhausted grants return their own registered denial. A requested ceiling is intersected with the current grant rather than refused. An ungranted domain fails domain_not_granted without revealing whether it holds entries, and unknown or foreign proposal IDs produce the same proposal_not_found. An unknown path answers not_found, an unexpected failure internal_error, and at a recipient route a provider that cannot reach its key storage or grant state answers not_ready; none of them says why. Each code's MCP form is on the MCP reference.

Migration does not return a destination through a handle_moved response, which is deliberately absent. A new provider requires new authorisation, and credentials are never redirected across origins.

References to other standards and projects describe intended technical alignment only and do not imply endorsement or partnership.

Read the complete error table, download the registry or inspect the exact schema.

Written against edition 1.0-draft-1: Error registry