Turn one endpoint into an OpenAPI 3 document
Enter a path, a method, parameters and response codes, and the tool writes a minimal OpenAPI 3 document in YAML that you can save as a file. If a brace variable in the path is not declared as a parameter, or a path parameter is declared but missing from the path, generation stops and names the mismatch. Status codes and the path are quoted so YAML does not read them as numbers.
3.0 and 3.1 spell the same idea differently. 3.1 aligns with JSON Schema 2020-12 and marks a nullable field with a type array, while 3.0 uses the nullable key. Switch the version select and the difference shows up in the output. The wording follows the OpenAPI Specification published by the OpenAPI Initiative, as of October 2026.
This tool writes only the skeleton. It does not build full property schemas, security schemes or component references, and it does not read an existing document to validate it. Which version you should target depends on the tooling around you, so check the generated YAML against your real implementation.
Frequently Asked Questions
It comes out as a minimal document with openapi, info and paths, so you can save it to a file and feed it to your tooling. Property schemas and security schemes are left empty, so you still have to fill them in for a real service document.
Follow the version your tooling supports. 3.1 aligns with JSON Schema 2020-12 while 3.0 uses a modified dialect, so even the nullable notation differs in the output.
Empty braces in the path and path variables that are not declared as parameters are both reported as errors, and generation stops. The message names the parameter that is missing.