{
  "id": "email-domain-readiness",
  "name": "Public email-domain DNS readiness",
  "description": "Inspect one public ASCII domain's live MX, null MX, or implicit A/AAAA fallback with resolver/time/TTL evidence. Domain only; no email address, mailbox, deliverability, disposable/free-provider or role classification. x402 only.",
  "category": "standards",
  "priceUsd": "0.002",
  "pricingStatus": "proposed-unverified",
  "pricing": {
    "unit": "one successful operation call",
    "proposedNominalUsd": "0.002",
    "sixDecimalTokenBaseUnits": "2000",
    "subscription": false,
    "includesPayerWalletOrNetworkFees": false,
    "liveQuoteVerified": false,
    "condition": "Actual SDK challenge is authoritative only within the caller's explicit authorization; configured six-decimal token peg is an operator assertion, not a conversion guarantee."
  },
  "intents": [
    "check email domain DNS readiness",
    "live MX record lookup",
    "detect null MX domain",
    "check implicit mail A AAAA fallback"
  ],
  "whenToUse": [
    "Inspect public-domain mail-routing DNS records with bounded live resolver evidence."
  ],
  "whenNotToUse": [
    "Full email validation, mailbox existence, SMTP delivery tests, disposable/free-provider/role classification, MX-host reachability, arbitrary DNS record types, private DNS, internationalized Unicode input, or guaranteed DNS freshness."
  ],
  "capabilities": [
    "email-domain-readiness",
    "public DNS MX",
    "null MX",
    "implicit A AAAA fallback",
    "NXDOMAIN",
    "resolver timestamp TTL"
  ],
  "related": [
    "url-inspect"
  ],
  "limits": {
    "queries": 3,
    "queryTimeoutMs": 1500,
    "totalTimeoutMs": 5000,
    "resolverResponseBytes": 32768,
    "recordsPerQuery": 64,
    "outputBytes": 32768
  },
  "errorCodes": [
    "INVALID_INPUT",
    "INVALID_DOMAIN",
    "UNSUPPORTED_DOMAIN",
    "DNS_BUSY",
    "DNS_TIMEOUT",
    "DNS_SERVFAIL",
    "DNS_UNAVAILABLE",
    "DNS_HTTP_ERROR",
    "DNS_TRUNCATED",
    "DNS_INVALID_RESPONSE",
    "DNS_INCONSISTENT_RESPONSE"
  ],
  "requirementsProfile": {
    "format": "declared-requirements-v1",
    "facts": {
      "execution.suppliedCode": false,
      "execution.remoteMutation": false,
      "execution.llmInference": false,
      "execution.paidMcp": false,
      "verification.semanticTruth": false,
      "verification.sourceAuthenticity": false,
      "verification.liveVulnerabilities": false,
      "numbers.arbitraryPrecisionJson": false,
      "numbers.model": "ieee754-binary64",
      "privacy.requestBodyPersisted": false,
      "execution.deterministic": false,
      "execution.networkAccess": true,
      "privacy.resultBodyPersisted": true,
      "payment.x402": true,
      "payment.mpp": false,
      "operation.id": "email-domain-readiness",
      "operation.category": "standards",
      "limit.httpRequestBytes": 131072,
      "limit.requestBytes": 131072,
      "limit.responseBytes": 524288,
      "limit.resultBytes": 32768,
      "limit.jsonDepth": 32,
      "limit.jsonNodes": 20000,
      "dns.profile": "public-email-domain-dns-v1",
      "dns.resolver": "https://dns.google/resolve",
      "dns.maxQueries": 3,
      "dns.domainOnly": true,
      "dns.mxHostAddresses": false,
      "dns.mailboxExistence": false,
      "dns.smtp": false,
      "dns.disposableClassification": false,
      "dns.applicationCache": false,
      "dns.snapshotReplay": true,
      "dns.snapshotRetentionHours": 24,
      "dns.uncertainSnapshotRetained": true,
      "input.domain.maxLength": 254,
      "input.domain.minLength": 3
    },
    "unknownPolicy": "Undeclared requirements are unknown, never compatible. Matching declared facts does not establish semantic fit or input validity.",
    "preflight": "/preflight"
  },
  "documentation": "/reference/tools/email-domain-readiness.md",
  "serviceContract": "/reference/services/email-domain-readiness.json",
  "errors": [
    {
      "status": 400,
      "meaning": "Malformed JSON, missing/invalid idempotency key, or payment identifier mismatch",
      "retry": "Correct the request before payment"
    },
    {
      "status": 402,
      "meaning": "Payment challenge or rejected payment",
      "retry": "Use official protocol SDK; inspect payment outcome before another payment"
    },
    {
      "status": 409,
      "meaning": "Idempotency conflict, duplicate proof, or PAYMENT_UNCERTAIN",
      "retry": "Keep original key, body, and proof; reconcile uncertainty with operator; never blindly repay"
    },
    {
      "status": 413,
      "meaning": "Input or generated output too large",
      "retry": "Reduce input; no payment attempted for validation failure"
    },
    {
      "status": 415,
      "meaning": "Unsupported media type or compression",
      "retry": "Send uncompressed application/json"
    },
    {
      "status": 422,
      "meaning": "Schema or service-specific semantic validation failure",
      "retry": "Correct input using returned error code; no payment attempted"
    },
    {
      "status": 429,
      "meaning": "Request/payment-attempt rate exceeded",
      "retry": "Wait for rate limit window; preserve existing payment identity"
    },
    {
      "status": 503,
      "meaning": "Payment configuration/provider/state unavailable, or live DNS preparation failed before settlement",
      "retry": "Check readiness; DNS preparation failures may retry the identical key/body/credential only; uncertainty requires reconciliation"
    }
  ],
  "numericPrecision": "JavaScript IEEE-754 numbers; use strings for large integer IDs/exact decimals where the schema accepts strings. No lossless numeric parsing.",
  "paymentWorkflow": {
    "discoveryOnly": false,
    "supportedProtocols": [
      "x402"
    ],
    "x402": {
      "credentialHeader": "PAYMENT-SIGNATURE",
      "challengeHeader": "PAYMENT-REQUIRED",
      "receiptHeader": "PAYMENT-RESPONSE",
      "version": 2,
      "scheme": "exact",
      "paymentIdentifier": "payment-identifier extension MUST equal the HTTP Idempotency-Key",
      "sdk": "@x402/core with @x402/evm"
    },
    "mpp": {
      "supported": false,
      "credentialHeader": "Authorization",
      "challengeHeader": "WWW-Authenticate",
      "receiptHeader": "Payment-Receipt",
      "method": "tempo",
      "intent": "charge",
      "sdk": "mppx",
      "tokenDecimals": 6
    },
    "steps": [
      "Check configured readiness and the exact service schema",
      "Generate a fresh random Idempotency-Key for this operation; never use a discovery probe fixture for purchases",
      "Send valid input without a credential to obtain the official protocol challenge",
      "Use the official SDK and authorized wallet to fulfill the challenge",
      "Retry only with identical key, body, protocol and credential",
      "On PAYMENT_UNCERTAIN stop and request operator reconciliation; never blindly pay again"
    ],
    "versionedRetries": "Request fingerprint includes service release version. Retries across a version upgrade can conflict; coordinate upgrades outside the 24-hour replay window and reconcile pending attempts.",
    "docs": "/llms.txt"
  },
  "method": "POST",
  "paths": {
    "x402": "/v1/x402/email-domain-readiness"
  },
  "inputSchema": {
    "$schema": "https://json-schema.org/draft/2020-12/schema",
    "type": "object",
    "properties": {
      "domain": {
        "type": "string",
        "minLength": 3,
        "maxLength": 254
      }
    },
    "required": [
      "domain"
    ],
    "additionalProperties": false
  },
  "outputSchema": {
    "type": "object",
    "required": [
      "operation",
      "version",
      "result",
      "provenance"
    ],
    "properties": {
      "operation": {
        "const": "email-domain-readiness",
        "type": "string"
      },
      "version": {
        "const": "0.29.0",
        "type": "string"
      },
      "result": {
        "$schema": "https://json-schema.org/draft/2020-12/schema",
        "type": "object",
        "properties": {
          "profile": {
            "type": "string",
            "const": "public-email-domain-dns-v1"
          },
          "domain": {
            "type": "string",
            "maxLength": 253
          },
          "canonicalDomain": {
            "type": "string",
            "maxLength": 253
          },
          "status": {
            "type": "string",
            "enum": [
              "mx_records",
              "null_mx",
              "implicit_mx",
              "no_mail_route",
              "nxdomain",
              "inconsistent_mx"
            ]
          },
          "mxRecords": {
            "maxItems": 64,
            "type": "array",
            "items": {
              "type": "object",
              "properties": {
                "preference": {
                  "type": "integer",
                  "minimum": 0,
                  "maximum": 65535
                },
                "exchange": {
                  "type": "string",
                  "maxLength": 253
                },
                "ttlSeconds": {
                  "type": "integer",
                  "minimum": 0,
                  "maximum": 2147483647
                }
              },
              "required": [
                "preference",
                "exchange",
                "ttlSeconds"
              ],
              "additionalProperties": false
            }
          },
          "implicitAddresses": {
            "maxItems": 128,
            "type": "array",
            "items": {
              "type": "object",
              "properties": {
                "type": {
                  "type": "string",
                  "enum": [
                    "A",
                    "AAAA"
                  ]
                },
                "address": {
                  "type": "string",
                  "maxLength": 45
                },
                "ttlSeconds": {
                  "type": "integer",
                  "minimum": 0,
                  "maximum": 2147483647
                }
              },
              "required": [
                "type",
                "address",
                "ttlSeconds"
              ],
              "additionalProperties": false
            }
          },
          "observations": {
            "minItems": 1,
            "maxItems": 3,
            "type": "array",
            "items": {
              "type": "object",
              "properties": {
                "name": {
                  "type": "string",
                  "maxLength": 253
                },
                "type": {
                  "type": "string",
                  "enum": [
                    "MX",
                    "A",
                    "AAAA"
                  ]
                },
                "status": {
                  "type": "string",
                  "enum": [
                    "NOERROR",
                    "NXDOMAIN"
                  ]
                },
                "canonicalName": {
                  "type": "string",
                  "maxLength": 253
                },
                "observedAt": {
                  "type": "string",
                  "format": "date-time",
                  "pattern": "^(?:(?:\\d\\d[2468][048]|\\d\\d[13579][26]|\\d\\d0[48]|[02468][048]00|[13579][26]00)-02-29|\\d{4}-(?:(?:0[13578]|1[02])-(?:0[1-9]|[12]\\d|3[01])|(?:0[469]|11)-(?:0[1-9]|[12]\\d|30)|(?:02)-(?:0[1-9]|1\\d|2[0-8])))T(?:(?:[01]\\d|2[0-3]):[0-5]\\d:[0-5]\\d(?:\\.\\d+)?(?:Z))$"
                },
                "resolver": {
                  "type": "string",
                  "const": "https://dns.google/resolve"
                },
                "resolverDnssecAuthenticated": {
                  "type": "boolean"
                },
                "records": {
                  "maxItems": 64,
                  "type": "array",
                  "items": {
                    "type": "object",
                    "properties": {
                      "name": {
                        "type": "string",
                        "maxLength": 253
                      },
                      "type": {
                        "type": "string",
                        "enum": [
                          "CNAME",
                          "MX",
                          "A",
                          "AAAA"
                        ]
                      },
                      "data": {
                        "type": "string",
                        "maxLength": 512
                      },
                      "ttlSeconds": {
                        "type": "integer",
                        "minimum": 0,
                        "maximum": 2147483647
                      }
                    },
                    "required": [
                      "name",
                      "type",
                      "data",
                      "ttlSeconds"
                    ],
                    "additionalProperties": false
                  }
                },
                "minimumAnswerTtlSeconds": {
                  "anyOf": [
                    {
                      "type": "integer",
                      "minimum": 0,
                      "maximum": 2147483647
                    },
                    {
                      "type": "null"
                    }
                  ]
                }
              },
              "required": [
                "name",
                "type",
                "status",
                "canonicalName",
                "observedAt",
                "resolver",
                "resolverDnssecAuthenticated",
                "records",
                "minimumAnswerTtlSeconds"
              ],
              "additionalProperties": false
            }
          },
          "externalRequests": {
            "type": "integer",
            "minimum": 1,
            "maximum": 3
          },
          "observedAt": {
            "type": "string",
            "format": "date-time",
            "pattern": "^(?:(?:\\d\\d[2468][048]|\\d\\d[13579][26]|\\d\\d0[48]|[02468][048]00|[13579][26]00)-02-29|\\d{4}-(?:(?:0[13578]|1[02])-(?:0[1-9]|[12]\\d|3[01])|(?:0[469]|11)-(?:0[1-9]|[12]\\d|30)|(?:02)-(?:0[1-9]|1\\d|2[0-8])))T(?:(?:[01]\\d|2[0-3]):[0-5]\\d:[0-5]\\d(?:\\.\\d+)?(?:Z))$"
          },
          "applicationDnsCache": {
            "type": "string",
            "const": "none"
          },
          "ttlPolicy": {
            "type": "string",
            "const": "remaining-resolver-answer-ttl-at-observation; replay-does-not-refresh"
          },
          "mailboxExistence": {
            "type": "string",
            "const": "not_checked"
          },
          "deliverability": {
            "type": "string",
            "const": "not_checked"
          },
          "mxHostAddresses": {
            "type": "string",
            "const": "not_checked"
          },
          "providerClassification": {
            "type": "string",
            "const": "not_checked"
          }
        },
        "required": [
          "profile",
          "domain",
          "canonicalDomain",
          "status",
          "mxRecords",
          "implicitAddresses",
          "observations",
          "externalRequests",
          "observedAt",
          "applicationDnsCache",
          "ttlPolicy",
          "mailboxExistence",
          "deliverability",
          "mxHostAddresses",
          "providerClassification"
        ],
        "additionalProperties": false
      },
      "provenance": {
        "type": "object",
        "required": [
          "inputSha256",
          "outputSha256",
          "deterministic",
          "externalRequests"
        ],
        "properties": {
          "inputSha256": {
            "type": "string",
            "pattern": "^[a-f0-9]{64}$"
          },
          "outputSha256": {
            "type": "string",
            "pattern": "^[a-f0-9]{64}$"
          },
          "deterministic": {
            "const": false
          },
          "externalRequests": {
            "type": "integer",
            "minimum": 1,
            "maximum": 3
          }
        }
      }
    },
    "additionalProperties": false
  },
  "exampleInput": {
    "domain": "example.com"
  },
  "exampleResponse": {
    "operation": "email-domain-readiness",
    "version": "0.29.0",
    "result": {
      "profile": "public-email-domain-dns-v1",
      "domain": "example.com",
      "canonicalDomain": "example.com",
      "status": "null_mx",
      "mxRecords": [
        {
          "preference": 0,
          "exchange": ".",
          "ttlSeconds": 300
        }
      ],
      "implicitAddresses": [],
      "observations": [
        {
          "name": "example.com",
          "type": "MX",
          "status": "NOERROR",
          "canonicalName": "example.com",
          "observedAt": "2026-10-04T00:00:00.000Z",
          "resolver": "https://dns.google/resolve",
          "resolverDnssecAuthenticated": false,
          "records": [
            {
              "name": "example.com",
              "type": "MX",
              "data": "0 .",
              "ttlSeconds": 300
            }
          ],
          "minimumAnswerTtlSeconds": 300
        }
      ],
      "externalRequests": 1,
      "observedAt": "2026-10-04T00:00:00.000Z",
      "applicationDnsCache": "none",
      "ttlPolicy": "remaining-resolver-answer-ttl-at-observation; replay-does-not-refresh",
      "mailboxExistence": "not_checked",
      "deliverability": "not_checked",
      "mxHostAddresses": "not_checked",
      "providerClassification": "not_checked"
    },
    "provenance": {
      "inputSha256": "b9e2a80fa92f8d5059ab90188e0691ad6730871a209cc337c7565593597fbd58",
      "outputSha256": "a7f5f263fc806b983907b619b6775fdeb681822afd1cea09f45cd835e53ac3a9",
      "deterministic": false,
      "externalRequests": 1
    }
  },
  "requiredHeaders": {
    "Content-Type": "application/json",
    "Idempotency-Key": "random 16–128 character operation identifier"
  },
  "fixedExample": "/reference/examples/email-domain-readiness.json",
  "execution": {
    "deterministic": false,
    "externalRequests": "snapshot provenance counts original 1-3 queries; replay preserves that count and adds zero new queries",
    "maxExternalRequests": 3,
    "resultSnapshotPersisted": true,
    "activation": {
      "requiredOperatorAssertion": "DNS_PROVIDER_TERMS_REVIEWED=true",
      "reason": "Commercial DNS wrapper/resale, upstream caching/redistribution and stored-replay retention require provider-terms review; this flag grants no permission",
      "runtimeAssessment": "not-evaluated"
    },
    "fixedExampleIsIllustrativeSnapshot": true,
    "requiresPayment": true,
    "supportsMcpExecution": false
  },
  "releaseSnapshot": {
    "format": "static-release-reference-v1",
    "sourceVersion": "0.29.0",
    "sourceRegistrySha256": "a2b5ec09bf6c38b9d2879d746a4fded374f5928b445377b0270ef6aa8e6cac65",
    "generatedAt": "2026-10-06T15:38:00Z",
    "releaseAcceptance": "not-verified-by-generator",
    "runtimeReadiness": "not-evaluated",
    "livePaymentsVerified": false,
    "indexingVerified": false,
    "apiOrigin": null,
    "notice": "Build-time release reference. Runtime readiness, deployment, payment settlement and external indexing are not evaluated here. Prices are proposed; this file cannot authorize execution or payment."
  }
}