{"id":"ia.api-errors","name":"API error responses","verify":{"command":"curl -s https://{domain}/api/isagentready-missing-check | jq -e '.status or .error'","rescan":"isagentready results {domain} --checkpoint ia.api-errors","expect":"exit code 0"},"fix":{"steps":[{"action":"Return application/problem+json for each 4xx and 5xx response of the API.","order":1,"language":"json","code_example":"{\"type\": \"https://example.com/problems/not-found\", \"title\": \"Not found\", \"status\": 404, \"detail\": \"No such resource\"}"}],"summary":"Return RFC 9457 problem details as JSON for API errors.","skill":{"name":"agent-protocols","anchor":"ia.api-errors"}},"category":"agent_protocols","aggregate":null,"references":[{"title":"RFC 9457: Problem Details for HTTP APIs","kind":"spec","url":"https://www.rfc-editor.org/rfc/rfc9457"}],"stage":"act","lifecycle":{"introduced":"2026-08-25","revised":[],"retired":null,"replaced_by":null},"methodology_version":"2026-10-22","evidence_tier":"supported","evidence_source":{"title":"agentready.org AR-ACT-02","url":"https://www.agentready.org/#act"},"why":"Agents call APIs programmatically and cannot recover from an HTML error page. A JSON problem-details body with a machine-readable code and a human-readable message lets them branch on failures instead of guessing.","profiles":["api_tool_readiness","agentic_commerce"],"score_role":"core","legacy_id":"4.22","i18n":{"nl":{"name":"API-foutresponses","steps":["Geef application/problem+json terug voor elke 4xx- en 5xx-response van de API."],"why":"Agents roepen API's programmatisch aan en kunnen niet herstellen van een HTML-foutpagina. Een JSON problem-details-body met een code en een bericht laat ze op fouten reageren.","fix_summary":"Geef RFC 9457 problem details als JSON terug bij API-fouten.","verify_expect":"exitcode 0"}},"ar_practice_ids":["AR-ACT-02"],"strength":"SHOULD","ar_mapping":"partial","evidence_type":"recommendation","detail_url":"https://isagentready.com/en/methodology/checkpoints/ia.api-errors","maturity":"recommended","applicability":{"mode":"detected_surface","condition":null,"surfaces":["api"]}}