{
  "$schema": "http://json-schema.org/draft-07/schema#",
  "$id": "https://observerprotocol.org/schemas/x402/v1.json",
  "title": "X402 Payment Credential Schema v1",
  "description": "W3C Verifiable Credential schema for x402-mediated payments. Issued by Observer Protocol after verifying both Coinbase facilitator attestation and on-chain USDC settlement on Base (or other x402-supported chain). Dual verification: facilitator endpoint as primary, Base RPC as ground truth.",
  "type": "object",
  "required": [
    "@context",
    "id",
    "type",
    "issuer",
    "validFrom",
    "validUntil",
    "credentialSubject",
    "credentialSchema",
    "proof"
  ],
  "properties": {
    "@context": {
      "type": "array",
      "minItems": 2,
      "items": { "type": "string" },
      "contains": { "enum": ["https://www.w3.org/ns/credentials/v2"] }
    },
    "id": {
      "type": "string",
      "pattern": "^urn:uuid:",
      "description": "Unique credential identifier"
    },
    "type": {
      "type": "array",
      "minItems": 2,
      "items": { "type": "string" },
      "allOf": [
        { "contains": { "const": "VerifiableCredential" } },
        { "contains": { "const": "X402PaymentCredential" } }
      ]
    },
    "issuer": {
      "type": "string",
      "pattern": "^did:",
      "description": "OP's issuer DID (did:web:observerprotocol.org)"
    },
    "validFrom": { "type": "string", "format": "date-time" },
    "validUntil": { "type": "string", "format": "date-time" },
    "credentialSubject": {
      "type": "object",
      "required": [
        "id",
        "counterparty",
        "paymentScheme",
        "network",
        "asset",
        "amount",
        "resource",
        "facilitator",
        "settlementTxHash",
        "paymentPayloadHash"
      ],
      "properties": {
        "id": {
          "type": "string",
          "pattern": "^did:",
          "description": "The payer agent's DID"
        },
        "counterparty": {
          "type": "string",
          "description": "DID or address of the resource provider (the x402 server)"
        },
        "paymentScheme": {
          "type": "string",
          "description": "The x402 payment scheme name (e.g. 'exact')",
          "examples": ["exact"]
        },
        "network": {
          "type": "string",
          "description": "CAIP-2 chain identifier for the settlement chain",
          "examples": ["eip155:8453", "eip155:1", "eip155:84532"]
        },
        "asset": {
          "type": "object",
          "required": ["address", "symbol"],
          "properties": {
            "address": {
              "type": "string",
              "description": "Token contract address on the settlement chain"
            },
            "symbol": {
              "type": "string",
              "description": "Token symbol (e.g. USDC)"
            }
          }
        },
        "amount": {
          "type": "string",
          "description": "Payment amount in atomic units (e.g. '1000000' for 1 USDC with 6 decimals). String to avoid float precision issues."
        },
        "resource": {
          "type": "string",
          "format": "uri",
          "description": "The URI of the resource paid for (the x402 protected endpoint)"
        },
        "facilitator": {
          "type": "string",
          "format": "uri",
          "description": "The x402 facilitator endpoint that settled the payment (e.g. Coinbase's facilitator URL)"
        },
        "settlementTxHash": {
          "type": "string",
          "description": "On-chain transaction hash of the USDC settlement on the target chain"
        },
        "paymentPayloadHash": {
          "type": "string",
          "description": "SHA-256 hash of the original signed x402 payment payload, for non-repudiation"
        },
        "verification": {
          "type": "object",
          "description": "Dual verification results. OP verifies both facilitator attestation and on-chain settlement independently.",
          "properties": {
            "facilitator_verified": {
              "type": "boolean",
              "description": "Whether the Coinbase facilitator endpoint confirmed the payment"
            },
            "onchain_verified": {
              "type": "boolean",
              "description": "Whether direct Base RPC query confirmed the USDC transfer on-chain"
            },
            "onchain_confirmations": {
              "type": "integer",
              "description": "Number of block confirmations at verification time"
            },
            "discrepancy": {
              "type": "boolean",
              "description": "True if facilitator and on-chain results disagree. OP surfaces this rather than hiding it.",
              "default": false
            }
          }
        },
        "agentId": {
          "type": "string",
          "description": "Raw agent identifier (OP internal)"
        },
        "timestamp": {
          "type": "string",
          "format": "date-time",
          "description": "ISO 8601 timestamp of the x402 payment"
        }
      }
    },
    "credentialSchema": {
      "type": "object",
      "required": ["id", "type"],
      "properties": {
        "id": { "type": "string", "pattern": "^https://observerprotocol.org/schemas/" },
        "type": { "const": "JsonSchema" }
      }
    },
    "proof": {
      "type": "object",
      "required": ["type", "created", "verificationMethod", "proofPurpose", "proofValue"],
      "properties": {
        "type": { "const": "Ed25519Signature2020" },
        "created": { "type": "string", "format": "date-time" },
        "verificationMethod": { "type": "string", "pattern": "^did:[a-z]+:.+#.+" },
        "proofPurpose": { "const": "assertionMethod" },
        "proofValue": { "type": "string", "pattern": "^z[1-9A-HJ-NP-Za-km-z]+$" }
      }
    }
  },
  "additionalProperties": false
}