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Pre-Payment Request Validation for x402 Endpoints
x402
Pre-Payment Request Validation for x402 Endpoints is a paid API for AI agents from k2so.wrong.systems, paid per call via x402, $0.002/call, status unknown (last checked 2026-10-28).
Returns a decision procedure and validation brief an agent should execute before paying an x402 endpoint, including parameter checks, credential verification, and skip-list guidance.
Price / call$0.002
Success—
StatusUnknown
How this service works
Agent-facing decision procedure for validating an x402 request before paying. Live probes show real costs: loyalspark charged then demanded a separate rwk_ API key, tripadvisor charged 0.013 then 400'd on a missing locationId, kadec0 charged 0.011 then 400'd on missing ids. This procedure gates each spend: extract required params from the contract, verify credential registration before first payment, type-check every parameter, re-read the 402 challenge price, and maintain a skip-list of
Output
A JSON object containing a boolean success flag, payment confirmation, a prose decision procedure brief for the agent, the generation source (llm, reasoning, or deterministic), the service slug, and an ISO-8601 timestamp — giving the agent a structured go/no-go signal before committing USDC.
Example use cases
Avoiding bad x402 charges on broken APIs
“I'm about to pay the TripAdvisor x402 endpoint but I've heard it sometimes charges you and then errors out — can you run the pre-payment validation check for a GET request to make sure I have the right params before I spend anything?”
Credential registration check before first payment
“This is the first time my agent is calling the loyalspark x402 endpoint — can you validate the pre-payment request for GET to confirm my credentials are registered and I won't get charged before being asked for a separate API key?”
Building an agent payment guard for an x402 pipeline
“I'm setting up an automated agent pipeline that calls several x402 APIs. Before each payment step, run the pre-payment validation procedure using GET so I can gate each spend and maintain a skip-list for endpoints that keep failing after payment.”
Technical details
Endpoint
GEThttps://k2so.wrong.systems/api/services/pre-payment-request-validation-for-x402-endpoint?utm_source=zero.xyzWhen to prefer
Use this endpoint when an agent is about to pay an x402 API and needs a structured, evidence-based go/no-go decision before spending USDC — especially for endpoints with a history of charging then returning errors (400s, missing param failures, or credential demands post-payment). Prefer it over ad-hoc manual checks when operating at scale across multiple x402 merchants or when building automated payment pipelines that need a skip-list mechanism.
Side effects
- Missing required 'input' object or 'method' field returns a 400-level error
- Invalid HTTP method value (e.g. POST) rejected by enum constraint
- Endpoint itself may charge $0.002 even if the target endpoint's validation result is a skip/fail
- Topic override not recognized may produce a generic rather than targeted brief
- Rate limits or unavailability of the underlying LLM/reasoning engine could delay or fail generation
Input
Schema · Request body
| Field | Type | Description |
|---|---|---|
| inputrequired | object | |
| output | object |
Tags
x402
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