{
  "id": "keywords-extract",
  "name": "Extract frequency keywords",
  "description": "Use to produce a small, reproducible frequency index for a document. Counts Unicode word-like spans containing letters, lowercases without stemming, optionally filters a fixed English stop list plus your stop words, and sorts by frequency then first occurrence. No semantic ranking, language detection, phrase extraction, or AI. First offsets refer to original UTF-16 text.",
  "category": "text",
  "priceUsd": "0.005",
  "pricingStatus": "proposed-unverified",
  "pricing": {
    "unit": "one successful operation call",
    "proposedNominalUsd": "0.005",
    "sixDecimalTokenBaseUnits": "5000",
    "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": [
    "extract frequent words",
    "rank document content words by frequency excluding common stopwords",
    "frequency keyword index"
  ],
  "whenToUse": [
    "Count word-like spans with optional stopword filtering."
  ],
  "whenNotToUse": [
    "Semantic keywords, sentiment, topic modeling, or language detection."
  ],
  "capabilities": [
    "keywords-extract",
    "extract frequent words",
    "rank document content words by frequency excluding common stopwords",
    "frequency keyword index"
  ],
  "related": [
    "text-metrics"
  ],
  "limits": {
    "requestBytes": 131072,
    "responseBytes": 524288,
    "jsonDepth": 32
  },
  "errorCodes": [
    "INVALID_INPUT",
    "INPUT_TOO_LARGE",
    "OUTPUT_TOO_LARGE"
  ],
  "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": true,
      "execution.networkAccess": false,
      "privacy.resultBodyPersisted": false,
      "payment.x402": true,
      "payment.mpp": true,
      "operation.id": "keywords-extract",
      "operation.category": "text",
      "limit.httpRequestBytes": 131072,
      "limit.requestBytes": 131072,
      "limit.responseBytes": 524288,
      "limit.resultBytes": 523264,
      "limit.jsonDepth": 32,
      "limit.jsonNodes": 20000,
      "input.text.maxLength": 100000,
      "input.limit.maximum": 100,
      "input.limit.minimum": 1,
      "input.minLength.maximum": 50,
      "input.minLength.minimum": 1,
      "input.stopWords.maxItems": 1000
    },
    "unknownPolicy": "Undeclared requirements are unknown, never compatible. Matching declared facts does not establish semantic fit or input validity.",
    "preflight": "/preflight"
  },
  "documentation": "/reference/tools/keywords-extract.md",
  "serviceContract": "/reference/services/keywords-extract.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",
      "mpp"
    ],
    "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": true,
      "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/keywords-extract",
    "mpp": "/v1/mpp/keywords-extract"
  },
  "inputSchema": {
    "$schema": "https://json-schema.org/draft/2020-12/schema",
    "type": "object",
    "properties": {
      "text": {
        "type": "string",
        "maxLength": 100000
      },
      "limit": {
        "default": 20,
        "type": "integer",
        "minimum": 1,
        "maximum": 100
      },
      "minLength": {
        "default": 3,
        "type": "integer",
        "minimum": 1,
        "maximum": 50
      },
      "useEnglishStopWords": {
        "default": true,
        "type": "boolean"
      },
      "stopWords": {
        "default": [],
        "maxItems": 1000,
        "type": "array",
        "items": {
          "type": "string",
          "minLength": 1,
          "maxLength": 100
        }
      }
    },
    "required": [
      "text"
    ],
    "additionalProperties": false
  },
  "outputSchema": {
    "type": "object",
    "required": [
      "operation",
      "version",
      "result",
      "provenance"
    ],
    "properties": {
      "operation": {
        "const": "keywords-extract",
        "type": "string"
      },
      "version": {
        "const": "0.29.0",
        "type": "string"
      },
      "result": {
        "$schema": "https://json-schema.org/draft/2020-12/schema",
        "type": "object",
        "properties": {
          "offsetUnit": {
            "type": "string",
            "const": "UTF-16 code units; zero-based, end-exclusive"
          },
          "totalCandidates": {
            "type": "integer",
            "minimum": 0,
            "maximum": 100000
          },
          "uniqueCandidates": {
            "type": "integer",
            "minimum": 0,
            "maximum": 100000
          },
          "keywords": {
            "maxItems": 100,
            "type": "array",
            "items": {
              "type": "object",
              "properties": {
                "keyword": {
                  "type": "string",
                  "minLength": 1,
                  "maxLength": 200000
                },
                "count": {
                  "type": "integer",
                  "minimum": 1,
                  "maximum": 100000
                },
                "firstOffset": {
                  "type": "integer",
                  "minimum": 0,
                  "maximum": 100000
                }
              },
              "required": [
                "keyword",
                "count",
                "firstOffset"
              ],
              "additionalProperties": false
            }
          }
        },
        "required": [
          "offsetUnit",
          "totalCandidates",
          "uniqueCandidates",
          "keywords"
        ],
        "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": true
          },
          "externalRequests": {
            "const": 0
          }
        }
      }
    },
    "additionalProperties": false
  },
  "exampleInput": {
    "text": "Agents call tools. Reliable tools help agents. Agents need reliable APIs.",
    "limit": 5
  },
  "exampleResponse": {
    "operation": "keywords-extract",
    "version": "0.29.0",
    "result": {
      "offsetUnit": "UTF-16 code units; zero-based, end-exclusive",
      "totalCandidates": 11,
      "uniqueCandidates": 7,
      "keywords": [
        {
          "keyword": "agents",
          "count": 3,
          "firstOffset": 0
        },
        {
          "keyword": "tools",
          "count": 2,
          "firstOffset": 12
        },
        {
          "keyword": "reliable",
          "count": 2,
          "firstOffset": 19
        },
        {
          "keyword": "call",
          "count": 1,
          "firstOffset": 7
        },
        {
          "keyword": "help",
          "count": 1,
          "firstOffset": 34
        }
      ]
    },
    "provenance": {
      "inputSha256": "e1093d85e7862788bef58f9027d758d036bcc705d5118f97af758a40bb8675b7",
      "outputSha256": "b6b220e1827e739ce3d78dd6b3978b76181d974a5e166c9f331843b591d5e677",
      "deterministic": true,
      "externalRequests": 0
    }
  },
  "requiredHeaders": {
    "Content-Type": "application/json",
    "Idempotency-Key": "random 16–128 character operation identifier"
  },
  "fixedExample": "/reference/examples/keywords-extract.json",
  "execution": {
    "deterministic": true,
    "externalRequests": 0,
    "maxExternalRequests": 0,
    "resultSnapshotPersisted": false,
    "fixedExampleIsIllustrativeSnapshot": false,
    "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."
  }
}