Error registry

spec 1.0-draft-1

The closed error registry covers implemented operational errors, specified recipient errors and specified refusals that reach only the person's own operations, such as the first-party sign-in and session refusals (A15.3) and the entry limit (A4.1). It does not claim those recipient or first-party endpoints exist. B4.3 governs how a recipient endpoint uses it.

Code	HTTP status	Title
`invalid_scope`	400	Invalid scope
`purpose_missing`	400	Purpose is required
`invalid_request`	400	Invalid request
`not_found`	404	Not found
`idempotency_conflict`	409	Idempotency key already used
`payload_too_large`	413	Request too large
`rate_limited`	429	Try again later
`internal_error`	500	Request could not be completed
`not_ready`	503	Service is not ready
`domain_not_granted`	403	Domain is not granted
`grant_revoked`	403	Grant is no longer active
`grant_expired`	403	Grant has expired
`grant_exhausted`	403	Grant limit reached
`dpop_required`	401	Sender proof is required
`dpop_invalid`	401	Sender proof is invalid
`safety_write_forbidden`	403	First-party confirmation is required
`inference_forbidden`	403	Inference is not permitted
`proposal_not_found`	404	Proposal was not found
`proposal_decided`	409	Proposal has already been decided
`value_rejected`	422	Value does not match the vocabulary
`capability_not_granted`	403	Capability is not granted
`advertising_ineligible`	403	Advertising permission is unavailable
`client_suspended`	403	Client is suspended
`entry_limit_reached`	409	Entry limit reached
`session_required`	401	Sign-in is required
`csrf_invalid`	403	Request could not be verified
`reauthentication_required`	403	Recent sign-in is required
`signup_unavailable`	403	Sign-up is not available
`sign_in_failed`	400	Sign-in failed

Download the registry and Problem Details schema. B3.4 gives each code's MCP form, or says that no agent operation raises it. No error includes submitted context, credentials or hidden-entry details.

OAuth and PDPP Core errors keep their own representation. The registry lists the ones the text cites under external without registering them. OAuth: invalid_request, invalid_client, invalid_grant, unauthorized_client, unsupported_grant_type, unsupported_response_type, invalid_scope, access_denied, server_error, login_required, consent_required, interaction_required, invalid_redirect_uri, invalid_client_metadata, invalid_request_uri, invalid_target, invalid_authorization_details, unsupported_token_type, invalid_token, invalid_dpop_proof, use_dpop_nonce. PDPP Core: grant_expired, grant_revoked, not_found, invalid_request, blob_not_found.

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