1ROOTnode

Web Bot Auth Signature Verifier (RFC 9421) art-129

Ed25519 signature verdict over the RFC 9421 signature base establishes whether the caller-captured request signature is genuine, ahead of the nonce and directory checks below.

MCP Call · verify_webbotauth_signature

{
  "jsonrpc": "2.0",
  "method": "tools/call",
  "params": {
    "name": "verify_webbotauth_signature",
    "arguments": {
      "covered_components": [
        { "name": "method", "value": "POST" },
        { "name": "@authority", "value": "api.example.com" },
        { "name": "@path", "value": "/agent/v1/execute" }
      ],
      "signature_params": "(\"method\" \"@authority\" \"@path\");created=1750000000;keyid=\"key-2026-06\";tag=\"web-bot-auth\";alg=\"ed25519\"",
      "signature_b64": "ruUab1uVdHazfuOcU0E4qLcTnOM2Z7zYHiluP5qxDZkKbw8EjPNarFHL7G2fS2DhnFH1xlpbihrIkOm8jwxIDA==",
      "public_key_jwk": { "kty": "OKP", "crv": "Ed25519", "x": "WrHvnND7oaWfvrGxUU3FNeJaQDwYj4K3e5fl0fH5p2g" },
      "alg": "ed25519",
      "expected_tag": "web-bot-auth",
      "created": 1750000000,
      "now_unix": 1750000060,
      "max_age_s": 3600
    }
  },
  "id": 1
}

2STEP 2node

Web Bot Auth Nonce & Replay-Window Checker art-593

Nonce format, the TAP created/expires spread, and caller-supplied replay-set membership are assessed next: a separate fact about the same captured request, independent of the signature verdict above.

MCP Call · check_webbotauth_nonce_replay

{
  "jsonrpc": "2.0",
  "method": "tools/call",
  "params": {
    "name": "check_webbotauth_nonce_replay",
    "arguments": {
      "nonce": "aB3dEfGhIjKlMnOpQrStUvWxYz012345",
      "created": 1750000000,
      "expires": 1750000300,
      "now_unix": 1750000060,
      "max_age_s": 3600,
      "seen_nonces": []
    }
  },
  "id": 2
}

3STEP 3node

JWKS Pinned-Directory Check art-609

The caller-supplied JWKS directory document's canonical digest is checked against the caller's own out-of-band pinned digest before the directory's internal shape is trusted by the next step.

MCP Call · check_jwks_pinned_directory

{
  "jsonrpc": "2.0",
  "method": "tools/call",
  "params": {
    "name": "check_jwks_pinned_directory",
    "arguments": {
      "directory_jwks": {
        "keys": [
          {
            "kty": "OKP",
            "crv": "Ed25519",
            "kid": "key-2026-06",
            "x": "WrHvnND7oaWfvrGxUU3FNeJaQDwYj4K3e5fl0fH5p2g"
          }
        ]
      },
      "pinned_digest": "45d28be3698cb02c2a658ecb15c292076254ca24cd797bc75a39dacd244a028d"
    }
  },
  "id": 3
}

4TERMINALnode

HTTP Signatures Directory Validator art-130

Terminal stage: JWKS directory shape and keyid resolution are validated on the same pinned document, completing the four-fact TAP verification surface.

MCP Call · validate_signature_directory

{
  "jsonrpc": "2.0",
  "method": "tools/call",
  "params": {
    "name": "validate_signature_directory",
    "arguments": {
      "well_known_path": "/.well-known/http-message-signatures-directory",
      "keyid": "key-2026-06",
      "directory_jwks": {
        "keys": [
          {
            "kty": "OKP",
            "crv": "Ed25519",
            "kid": "key-2026-06",
            "x": "WrHvnND7oaWfvrGxUU3FNeJaQDwYj4K3e5fl0fH5p2g"
          }
        ]
      }
    }
  },
  "id": 4
}

Visa TAP Agent Verification (RFC 9421 Web Bot Auth + Nonce + JWKS Pin)