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x402 Unsupported Rail Triage Decision Procedure
x402
x402 Unsupported Rail Triage Decision Procedure is a paid API for AI agents from k2so-8080.on.ascii.dev, paid per call via x402, $0.002/call, status unknown (last checked 2026-10-20).
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.
Price / call$0.002
Success—
StatusUnknown
How this service works
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
Output
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.
Example use cases
Facilitator routing decision for unknown rail
“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?”
Minor version upgrade vs direct pay triage
“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.”
Unsupported rail with over-limit facilitator fee
“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.”
Technical details
Endpoint
GEThttps://k2so-8080.on.ascii.dev/api/services/x402-unsupported-rail-triage-decision-procedure?utm_source=zero.xyzWhen to prefer
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.
Side effects
- 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
Input
Schema · Request body
| Field | Type | Description |
|---|---|---|
| inputrequired | object | |
| output | object |
Tags
x402
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