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Agent Contract Proof Verifier
x402
Agent Contract Proof Verifier is a paid API for AI agents from agent-contract-proof.mattskowronis.workers.dev, paid per call via x402, $0.01/call, status unknown (last checked 2026-09-15).
Compares an agent's advertised contract with its live x402 payment challenge and returns deterministic cryptographic proof of consistency or change.
Price / call$0.01
Success—
StatusUnknown
How this service works
Compare an agent's advertised contract with its live x402 challenge and return deterministic proof.
Output
Returns a deterministic proof object indicating whether the agent's live x402 challenge matches its advertised contract, including a computed contract_hash, a match/mismatch status, and evidence of any contract change if an expected_hash was provided.
Example use cases
Audit agent before payment
“Before my workflow sends payment to the agent at https://trading-agent.example.com, can you verify its live x402 challenge matches its advertised contract and give me proof it hasn't changed?”
Detect contract drift in CI
“In my continuous integration pipeline, check whether the agent at https://data-agent.example.com still serves the same x402 contract as the hash 9b8a7f6e5d4c3b2a1f0e9d8c7b6a5f4e3d2c1b0a9f8e7d6c5b4a3f2e1d0c9b — flag it if the contract has drifted.”
Prove contract consistency to a client
“My client wants proof that the agent at https://inference-agent.example.com using POST is serving exactly the x402 contract it claims — can you run the contract proof check and return the deterministic result?”
Technical details
Endpoint
POSThttps://agent-contract-proof.mattskowronis.workers.dev/v1/verifyWhen to prefer
Use this endpoint when you need cryptographic, deterministic proof that an x402-compatible agent's live payment challenge matches its publicly advertised contract spec — especially before trusting an agent with payment, automating workflows that depend on contract stability, or auditing for tampering or drift. Prefer this over manual inspection when you need a verifiable, machine-readable proof artifact.
Side effects
- Agent URL is unreachable or returns a non-402 response — verification cannot proceed
- URL does not serve an x402 challenge — endpoint returns an error indicating no payment challenge found
- expected_hash is provided but malformed (not 64 hex characters) — request rejected with validation error
- Agent contract has changed — mismatch proof returned, not an error, but signals drift
- Network timeout contacting the target agent — returns a connectivity failure
- Invalid HTTP method specified — may fall back to GET or return an error
Input
Schema · Request body
| Field | Type | Description |
|---|---|---|
| url | string | Public HTTP or HTTPS agent/API URL. An origin URL may be resolved through discovery metadata. |
| method | string | Optional method to probe. If omitted, the advertised method is used, then GET as a fallback. |
| expected_hash | string | Optional previous contract_hash. A mismatch proves the public contract changed. |
Tags
x402
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