OpenAPI Generator
Generate validated OpenAPI 3.1 endpoint specifications from methods, paths, parameters, and sample request/response JSON. Instant YAML/JSON output.
About this openapi generator
This focused API design tool synthesizes a validated OpenAPI 3.1 operation draft from user-defined HTTP parameters, authentication configurations, and request/response JSON payloads. It automatically infers requestBody and response content schemas and validates the emitted YAML/JSON against the official OpenAPI specification. All processing runs in the client browser with zero server telemetry.
OpenAPI 3.1 alignment with JSON Schema Draft 2020-12
OpenAPI 3.1.0 resolved a long-standing incompatibility by replacing its custom Schema Object dialect with a full-compliant JSON Schema Draft 2020-12 subset. This means OpenAPI 3.1 schemas can include if/then/else conditionals, $defs references, unevaluatedProperties, and prefixItems for tuple validation—features that were unavailable or behaved differently in OpenAPI 3.0. Tools that consume OpenAPI 3.1 documents must use a JSON Schema Draft 2020-12 validator for the Schema Object rather than a Draft-04 or Draft-07 validator used with OpenAPI 3.0, which is a breaking change for many open-source code-generation and documentation tools.
API design principles and operation granularity
RESTful API design practice recommends organizing operations around resources (nouns) rather than actions (verbs), using HTTP method semantics (GET for read, POST for create, PUT/PATCH for update, DELETE for remove), and designing each operation to be stateless and idempotent where possible. OpenAPI operationIds should be stable across specification versions because they are used as function names by SDK generators, as test case identifiers in contract testing tools, and as routing labels in API gateway configurations. Changing an operationId is a breaking change for any generated client that uses the old identifier. It automatically infers requestBody and response content schemas and validates the emitted YAML/JSON against the official OpenAPI specification. All processing runs in the client browser with zero server telemetry.
Worked POST endpoint example
A POST to /users with email and role fields becomes a requestBody with an application/json schema. A 201 response receives its own schema and exact example.
Bearer, Basic, or API-key selection creates an explicit security scheme and operation requirement. No secret value is placed in the document.
What the generator deliberately does not invent
A response sample cannot reveal authorization policy, pagination, rate limits, retries, every error response, or conditional validation. The output is labeled a draft and the readiness report flags important omissions.
Parameter-line format
- Enter one query or header parameter per line as name:type:required|optional:description.
- Supported primitive parameter types are string, integer, number, and boolean.
- Path placeholders such as {id} automatically produce required string path parameters.
- Review generated operationId, descriptions, error responses, examples, and authentication before publishing.
OpenAPI Specification · Content owner: CZOA Tools · Review methodology
How to use it
- Enter the server URL, HTTP method, path, operation name, and summary.
- Describe query and header parameters and paste representative request and response JSON.
- Choose authentication, status code, content type, and YAML or JSON output.
- Generate the draft, fix all blocking errors, and review every warning before integrating it.
Frequently asked questions
How does OpenAPI Generator build a document?+
The page collects title, server URL, method, path, summary, operation ID, parameter rows, request and response JSON, status, authentication, content type, and YAML or JSON output. It creates an OpenAPI 3.1 draft and validates the generated document.
Can you show an input and its result?+
With the visible default fields, it returned an OpenAPI 3.1 YAML document for POST /users, operationId createUser, a quoted 201 response, request and response schemas, a query notify parameter, and bearer security declaration.
What does generated validation establish?+
It establishes that the generated draft passes this page’s OpenAPI and design checks for the supplied controls. It does not prove a remote endpoint exists, that authorization works, that example values are live data, or that every business error is documented.
Which input boundaries matter?+
A path must begin with slash, contain no whitespace, query, fragment, or malformed parameter braces, and the method must be one of the visible supported verbs. JSON examples and parameter row syntax are parsed rather than copied as unverified prose.