OpenAPI Payload Validator

x402

OpenAPI Payload Validator is a paid API for AI agents from agent402.tools, paid per call via x402, $0.001/call, status unknown (last checked 2026-09-14).

Validates a JSON payload against the request or response schema for a specific operation in an OpenAPI 3.x or Swagger 2.x specification

Price / call$0.001

Seller volume →—

Success—

StatusUnknown

How this service works

Validate a JSON payload against the request or response schema for one operation in an OpenAPI 3.x or Swagger 2.x spec. Locate the operation by operationId or method+path; choose `part: "request"` or `part: "response"` (status defaults to the first 2xx). Deterministic subset of JSON Schema: type, required, enum, properties, items, additionalProperties:false, oneOf/anyOf/allOf, $ref-detection (not dereferenced).

Output

A validation result indicating whether the provided JSON payload conforms to the request or response schema for the specified API operation, including any schema validation errors or constraint violations found.

Example use cases

Example prompt

“Can you validate this JSON payload against the request schema for the 'createUser' operation in my OpenAPI spec? Here's the spec and the payload I want to check — let me know if it's valid or what errors it has.”

Technical details

Endpoint

POSThttps://agent402.tools/api/openapi-validate-payload

When to prefer

Use this endpoint when you need to programmatically validate a JSON payload against a specific OpenAPI 3.x or Swagger 2.x operation schema — either request body or response body — without running the actual API. Ideal for pre-flight request validation, CI/CD pipeline checks, contract testing, or debugging schema mismatches. Prefer this over generic JSON Schema validators when the schema is embedded in an OpenAPI spec and you want to leverage the spec's full operation context including operationId lookup.

Side effects

Invalid or unparseable OpenAPI/Swagger spec document — returns error indicating spec is malformed
operationId not found in spec — returns error that the operation could not be located
Neither operationId nor method+path provided — returns error that operation cannot be identified
Invalid value for 'part' field (not 'request' or 'response') — returns validation or parse error
No matching schema found for the given status code in response validation — may default or error
Malformed payload JSON — returns parse error
Spec references external $refs that cannot be resolved — may return incomplete validation or error

Input

Schema · Request body

Field	Type	Description
part	—	Schema to validate against: "request" or "response"
path	—	Path template (use with `method` if no operationId)
spec	—	OpenAPI/Swagger document (object or JSON string)
method	—	HTTP method (use with `path` if no operationId)
status	—	Response status when part="response" (defaults to first 2xx)
payload	—	JSON value to validate
operationId	—	operationId to validate against (preferred)

Output

Schema · Response

{
  "type": "json",
  "example": {
    "valid": false,
    "errors": [
      {
        "path": "",
        "rule": "required",
        "message": "missing required field: email"
      },
      {
        "path": ".age",
        "rule": "type",
        "message": "expected integer, got string"
      },
      {
        "path": ".extra",
        "rule": "additionalProperties",
        "message": "unexpected property: extra"
      }
    ],
    "schemaPresent": true
  }
}

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How this service works

Output

Technical details

Endpoint

POSThttps://agent402.tools/api/openapi-validate-payload

When to prefer

Side effects

Invalid or unparseable OpenAPI/Swagger spec document — returns error indicating spec is malformed
operationId not found in spec — returns error that the operation could not be located
Neither operationId nor method+path provided — returns error that operation cannot be identified
Invalid value for 'part' field (not 'request' or 'response') — returns validation or parse error
No matching schema found for the given status code in response validation — may default or error
Malformed payload JSON — returns parse error
Spec references external $refs that cannot be resolved — may return incomplete validation or error

Input

Schema · Request body

Field	Type	Description
part	—	Schema to validate against: "request" or "response"
path	—	Path template (use with `method` if no operationId)
spec	—	OpenAPI/Swagger document (object or JSON string)
method	—	HTTP method (use with `path` if no operationId)
status	—	Response status when part="response" (defaults to first 2xx)
payload	—	JSON value to validate
operationId	—	operationId to validate against (preferred)

Output

Schema · Response

{
  "type": "json",
  "example": {
    "valid": false,
    "errors": [
      {
        "path": "",
        "rule": "required",
        "message": "missing required field: email"
      },
      {
        "path": ".age",
        "rule": "type",
        "message": "expected integer, got string"
      },
      {
        "path": ".extra",
        "rule": "additionalProperties",
        "message": "unexpected property: extra"
      }
    ],
    "schemaPresent": true
  }
}