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Webhook Signature Fixture Lab
x402
Webhook Signature Fixture Lab is a paid API for AI agents from mcp-factory.bowling-anthony.workers.dev, paid per call via x402, $0.03/call, status unknown (last checked 2026-09-14).
Generates test fixtures for HMAC-SHA256 webhook signature verification, including valid, tampered, and wrong-signature cases
Price / call$0.03
Success—
StatusUnknown
How this service works
Customer-input analysis tools with per-call x402 v2 USDC payments on Base. Discovery and examples are free.
Output
Returns a JSON object containing: the generated X-Hub-Signature-256 header value, an array of named test fixtures (valid, tampered_payload, wrong_signature) each with their header, payload, and expected validation outcomes (expected_accepted, expected_signature_valid, expected_time_valid), a verification field, and the SHA-256 hash of the payload. Each fixture specifies whether it should be accepted and whether the signature is valid, enabling automated test assertions.
Example use cases
Webhook handler unit test suite
“I'm building a GitHub webhook handler and need test fixtures — generate valid, tampered, and wrong-signature test cases for the payload 'POST /deploy triggered' using my secret 'mysecretkey123' so I can write unit tests for my X-Hub-Signature-256 verification.”
Security regression testing for webhooks
“Before shipping my new webhook endpoint, can you generate a set of HMAC-SHA256 fixture cases for the payload '{"event":"order.completed","id":42}' with secret 'prod-secret-abc' so I can confirm my signature validation rejects tampered and invalid signatures?”
Debugging webhook signature mismatch
“My webhook receiver keeps rejecting valid signatures and I don't know why — can you generate fixture test cases for the payload 'user.created' with secret 'webhook-secret-xyz' so I can compare the expected sha256 hash against what my code produces?”
Technical details
Endpoint
POSThttps://mcp-factory.bowling-anthony.workers.dev/webhook-signature-fixture-lab/analyzeWhen to prefer
Choose this endpoint when you need to generate comprehensive, ready-to-use HMAC-SHA256 webhook signature test fixtures — especially for GitHub-style X-Hub-Signature-256 verification. It is ideal for developers who want deterministic test vectors covering valid, tampered, and invalid signature scenarios without writing the crypto logic themselves. Prefer this over manual fixture creation when you need multiple edge-case scenarios in a single call.
Side effects
- Missing or invalid payload body returns error
- Missing secret key causes signature generation failure
- Malformed request body results in 400-level error
- Payment failure (x402) blocks call execution
- Insufficient USDC balance prevents call from completing
Output
Schema · Response
{
"type": "json",
"example": {
"ok": true,
"scope": "generated_fixtures_only",
"header": {
"name": "X-Hub-Signature-256",
"value": "sha256=757107ea0eb2509fc211221cce984b8a37570b6d7586c22c46f4379c8b043e17"
},
"fixtures": [
{
"name": "valid",
"header": {
"name": "X-Hub-Signature-256",
"value": "sha256=757107ea0eb2509fc211221cce984b8a37570b6d7586c22c46f4379c8b043e17"
},
"payload": "Hello, World!",
"expected_accepted": true,
"expected_time_valid": null,
"expected_signature_valid": true
},
{
"name": "tampered_payload",
"header": {
"name": "X-Hub-Signature-256",
"value": "sha256=757107ea0eb2509fc211221cce984b8a37570b6d7586c22c46f4379c8b043e17"
},
"payload": "Hello, World!!",
"expected_accepted": false,
"expected_time_valid": null,
"expected_signature_valid": false
},
{
"name": "wrong_signature",
"header": {
"name": "X-Hub-Signature-256",
"value": "sha256=057107ea0eb2509fc211221cce984b8a37570b6d7586c22c46f4379c8b043e17"
},
"payload": "Hello, World!",
"expected_accepted": false,
"expected_time_valid": null,
"expected_signature_valid": false
}
],
"verification": null,
"payload_sha256": "dffd6021bb2bd5b0af676290809ec3a53191dd81c7f70a4b28688a362182986f"
}
}Tags
x402
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