Pay-per-Verify: an agent pays $0

[
  {
    "scheme": "exact",
    "network": "eip155:8453",
    "payTo": "0xC13789e82661635d9Cea38a53A0390CF9939ef4f",
    "asset": "0x833589fCD6eDb6E08f4c7C32D4f71b54bdA02913",
    "amount": "10000",
    "maxTimeoutSeconds": 300
  },
  {
    "scheme": "exact",
    "network": "eip155:8453",
    "payTo": "0xC13789e82661635d9Cea38a53A0390CF9939ef4f",
    "asset": "0x833589fCD6eDb6E08f4c7C32D4f71b54bdA02913",
    "amount": "10000",
    "maxTimeoutSeconds": 300
  }
]

{
  "bazaar": {
    "body": {
      "message_b64": "BASE64_BYTES",
      "public_key": "BASE64_PK",
      "signature": "BASE64_SIG"
    },
    "bodyType": "json",
    "description": "Pay-per-Verify: an agent pays $0.01 to verify a post-quantum (ML-DSA-65 / Dilithium-3 or Dilithium-2, NIST FIPS 204; scheme auto-detected by size) signature over a message against a public key. A generic machine-to-machine PQC proof primitive for autonomous agents. x402-native.",
    "info": {
      "input": {
        "body": {
          "message_b64": "BASE64_BYTES",
          "public_key": "BASE64_PK",
          "signature": "BASE64_SIG"
        },
        "bodyType": "json",
        "method": "POST",
        "type": "http"
      },
      "output": {
        "example": {
          "algorithm": "ml-dsa-65",
          "valid": true,
          "verified_algorithm": "dilithium2"
        },
        "type": "json"
      }
    },
    "method": "POST",
    "output": {
      "example": {
        "algorithm": "ml-dsa-65",
        "valid": true,
        "verified_algorithm": "dilithium2"
      },
      "schema": {
        "properties": {
          "algorithm": {
            "description": "ml-dsa-65 — algorithm of THIS route's attestation signature over the verdict (NOT necessarily the client input scheme; see verified_algorithm).",
            "type": "string"
          },
          "algorithm_label": {
            "description": "ML-DSA-65 / Dilithium-3 (NIST FIPS 204)",
            "type": "string"
          },
          "attestation_digest": {
            "description": "sha256 hex over JSON({valid, verified_algorithm, message_b64, message_hash, signature: input_signature, public_key: input_public_key}) — reconstructible from this response.",
            "type": "string"
          },
          "input_public_key": {
            "description": "The exact base64 client public key that was verified (echoed for attestation_digest reconstruction).",
            "type": "string"
          },
          "input_signature": {
            "description": "The exact base64 client signature that was verified (echoed so a third party can recompute attestation_digest from this response alone).",
            "type": "string"
          },
          "message_b64": {
            "description": "The exact base64 bytes that were verified (echoed for reproducibility).",
            "type": "string"
          },
          "payment": {
            "description": "Settlement receipt (scheme, network, asset, txHash, payer, settled).",
            "type": "object"
          },
          "public_key": {
            "description": "Base64 ML-DSA-65 public key (1952 bytes) that verifies the attestation signature. Null if the served signer was unavailable.",
            "type": "string"
          },
          "served_signature_error": {
            "description": "Present only if the served attestation signer failed; the verdict is still authoritative and paid.",
            "type": "string"
          },
          "signature": {
            "description": "Base64 ML-DSA-65 / Dilithium-3 (NIST FIPS 204) signature (3309 bytes) by this server over the EXACT bytes echoed in `signed_message` = FRACTALAI-x402-served-v1\\nx402-verify-proof\\n<attestation_digest> (route-separated, 3 lines), attesting the verdict. Verify offline: ml_dsa65.verify(b64(signature), utf8(signed_message), b64(public_key)). Null (with served_signature_error) if the served signer was momentarily unavailable — the paid verdict is still served.",
            "type": "string"
          },
          "signed_message": {
            "description": "The EXACT UTF-8 bytes the served signature covers (FRACTALAI-x402-served-v1\\nx402-verify-proof\\n<attestation_digest>). Pass verbatim to ml_dsa65.verify — do not reconstruct it yourself.",
            "type": "string"
          },
          "valid": {
            "description": "True iff the supplied client signature (ML-DSA-65 or Dilithium-2, auto-detected) is valid over the message for the public key.",
            "type": "boolean"
          },
          "verified_algorithm": {
            "description": "The DETECTED scheme of the CLIENT input signature that was verified: ml-dsa-65 or dilithium2.",
            "type": "string"
          },
          "verified_algorithm_label": {
            "description": "Human label of verified_algorithm, e.g. \"ML-DSA-65 / Dilithium-3 (NIST FIPS 204)\" or \"Dilithium-2 (NIST FIPS 204)\".",
            "type": "string"
          }
        },
        "required": [
          "valid",
          "algorithm",
          "verified_algorithm",
          "input_signature",
          "input_public_key"
        ],
        "type": "object"
      },
      "type": "json"
    },
    "route_key": "POST /api/x402/verify-proof",
    "schema": {
      "$schema": "https://json-schema.org/draft/2020-12/schema",
      "properties": {
        "input": {
          "additionalProperties": false,
          "properties": {
            "body": {
              "type": "object"
            },
            "bodyType": {
              "enum": [
                "json",
                "form-data",
                "text"
              ],
              "type": "string"
            },
            "headers": {
              "additionalProperties": {
                "type": "string"
              },
              "type": "object"
            },
            "method": {
              "enum": [
                "POST",
                "PUT",
                "PATCH"
              ],
              "type": "string"
            },
            "queryParams": {
              "additionalProperties": {
                "type": "string"
              },
              "type": "object"
            },
            "type": {
              "const": "http",
              "type": "string"
            }
          },
          "required": [
            "type",
            "method",
            "bodyType",
            "body"
          ],
          "type": "object"
        },
        "output": {
          "properties": {
            "example": {
              "type": "object"
            },
            "type": {
              "type": "string"
            }
          },
          "required": [
            "type"
          ],
          "type": "object"
        }
      },
      "required": [
        "input"
      ],
      "type": "object"
    },
    "serviceName": "FractalAI Verify",
    "tags": [
      "verify",
      "signature",
      "post-quantum",
      "primitive",
      "ml-dsa-65"
    ],
    "type": "http"
  }
}

curl "https://fractalai.net.co/api/x402/verify-proof"
# -> 402 Payment Required, accepts[] lists how to pay
# retry with a PAYMENT-SIGNATURE (or PAYMENT header) once paid

const res = await fetch("https://fractalai.net.co/api/x402/verify-proof");
if (res.status === 402) {
  const { accepts } = await res.json();
  // pay one of accepts[] via an x402 client, then retry with the payment header
}

import httpx
res = httpx.get("https://fractalai.net.co/api/x402/verify-proof")
if res.status_code == 402:
    accepts = res.json()["accepts"]
    # pay one of accepts[] via an x402 client, then retry with the payment header