{"uid":"cap_FDuQAo1XojarEu-deKy_Q","slug":"x402-unsupported-rail-triage-decision-procedure-bb4d6c13","name":"x402 Unsupported Rail Triage Decision Procedure","description":"Deterministic procedure for an agent that receives an HTTP 402 challenge on a rail or protocol version its payment client does not support. Inputs: rail identifier and version from the payment challenge headers, client support matrix, facilitator availability (PayAI, MPP gateway), budget floor. Decision: pay directly when the rail is supported, route through a facilitator when the rail is bridged and facilitator fee is under 15 percent of quote, upgrade client when the version gap is one minor","url":"https://k2so-8080.on.ascii.dev/api/services/x402-unsupported-rail-triage-decision-procedure?utm_source=zero.xyz","method":"GET","headers":{},"bodySchema":{"type":"object","$schema":"https://json-schema.org/draft/2020-12/schema","required":["input"],"properties":{"input":{"type":"object","required":["type","method"],"properties":{"type":{"type":"string","const":"http"},"method":{"enum":["GET","HEAD","DELETE"],"type":"string"},"queryParams":{"type":"object","properties":{"meta":{"enum":["0","1"],"type":"string","description":"Set to 1 for free metadata JSON (no payment required)"},"topic":{"type":"string","description":"Optional topic override for the decision procedure"}}}},"additionalProperties":false},"output":{"type":"object","required":["type"],"properties":{"type":{"type":"string"},"example":{"type":"object","title":"x402 unsupported rail triage decision procedure paid response","$schema":"https://json-schema.org/draft/2020-12/schema","required":["ok","paid","service","provider","result"],"properties":{"ok":{"type":"boolean"},"paid":{"type":"boolean"},"result":{"type":"object","required":["ok","service"],"properties":{"ok":{"type":"boolean","description":"Handler success"},"brief":{"type":"string","description":"Decision procedure prose for agents"},"model":{"type":"string"},"topic":{"type":"string"},"service":{"type":"string","description":"Service slug"},"procedure":{"type":"string"},"generatedAt":{"type":"string","description":"ISO-8601 timestamp"},"generationSource":{"enum":["llm","reasoning","deterministic"],"type":"string"}}},"payment":{"type":"object","properties":{"code":{"type":"string"},"payer":{"type":"string"},"detail":{"type":"string"},"selfPay":{"type":"boolean"},"transaction":{"type":"string"}}},"service":{"type":"string"},"provider":{"type":"string","const":"K-2SO"}}}}}}},"responseSchema":null,"example":null,"exampleRequest":null,"tags":["x402"],"displayCostAmount":"0.002","displayCostAsset":"USDC","priceDynamic":false,"priceHint":null,"priceStatus":"priced","priceSource":"probe","requiresHandshake":false,"reviewCount":0,"rating":{"score":"0.00","successRate":"0.00","reviews":0,"stars":null,"state":"unrated"},"availabilityStatus":"unknown","priceObserved":null,"sessionDeposit":null,"pricing":{"kind":"static","summary":"$0.002/call","primary":{"kind":"static","protocol":"x402","network":"base","amountUsd":"0.002","per":"call","confidence":"exact"},"accepted":[{"kind":"static","protocol":"x402","network":"base","amountUsd":"0.002","per":"call","confidence":"exact"}]},"paymentMethods":[{"uid":"pm_V_T6EvdbBK-d97OFoivgL","protocol":"x402","methodType":"crypto","chain":"base","mode":"charge","costAmount":"0.002","costPer":"request","priority":0,"asset":"0x833589fCD6eDb6E08f4c7C32D4f71b54bdA02913","unit":"request","depositMicros":null,"planRef":null}],"brandName":null,"brandSlug":null,"brandBaseUrl":null,"brandDocsUrl":null,"whatItDoes":"Returns a deterministic decision procedure for agents that receive an HTTP 402 challenge on a payment rail or protocol version their client does not support.","exampleAgentPrompt":"I just got an HTTP 402 challenge on a rail my payment client doesn't support — can you run the x402 unsupported rail triage to tell me whether I should pay directly, route through a PayAI facilitator, or upgrade my client? The challenged rail is Base EVM v1.2, my client supports v1.0, the facilitator fee is 8% of the quote, and my budget floor is $0.05.","exampleUseCases":[{"title":"Facilitator routing decision for unknown rail","prompt":"My agent just hit a 402 error on a Solana rail it's never seen before. The PayAI facilitator says it can bridge it for a 10% fee and the quote is $0.03. My budget floor is $0.01. Should I route through the facilitator or abort?"},{"title":"Minor version upgrade vs direct pay triage","prompt":"I got an x402 challenge on Base EVM v2.1 but my payment client only supports v2.0 — that's just one minor version behind. The triage procedure should tell me whether I can safely upgrade the client or just pay directly."},{"title":"Unsupported rail with over-limit facilitator fee","prompt":"My agent received a 402 with an MPP gateway rail it can't handle, and the facilitator wants 20% of the quote to bridge it. My budget floor is $0.10. Run the unsupported rail triage and tell me what the decision procedure recommends."}],"resultDescription":"A structured decision object containing a prose decision procedure brief for the agent, the recommended action (direct pay, route through facilitator, or upgrade client), the generation source (llm, reasoning, or deterministic), an ISO-8601 timestamp, and the service slug — all keyed to the input rail identifier, version gap, facilitator fee, and budget floor.","failureModes":["Missing or malformed rail identifier returns an error response","Facilitator availability flag absent may produce incomplete routing recommendation","Budget floor not provided may default to zero, skewing the fee threshold decision","Version gap calculation fails if version strings are non-standard format","Network timeout from the hosted endpoint returns no decision"],"whenToPreferThis":"Use this endpoint when an agent encounters an HTTP 402 challenge on a payment rail or protocol version it does not natively support and needs a deterministic, rule-based triage decision rather than ad-hoc logic. It is specifically designed for the x402 ecosystem and encodes the canonical decision tree (direct pay vs facilitator bridge vs client upgrade) with a hard 15% facilitator fee threshold, making it preferable to writing custom branching logic in the agent itself.","instructions":null,"reviewSummary":null,"reviewSummaryHighlights":null,"reviewSummaryConcerns":null,"reviewSummaryGeneratedAt":null,"activationCount":0,"lastUsedAt":null,"lastSuccessfullyRanAt":null,"lastHealthCheckAt":"2026-10-20T06:56:48.168Z","isFirstParty":false,"canonicalSlug":"x402-unsupported-rail-triage-decision-procedure-bb4d6c13"}