OpenAPI to OpenAI Functions

Do you have an OpenAPI file or URL and want to use it in your Assistants API or OpenAI Function Calling? Look no further.

Disclaimer

This is a quick and dirty parser for OpenAPI spec to OpenAI Functions. It currently does not resolve $ref pointers.

Quick Start

pnpm add openapi-to-functions

import { convertRawOpenAPISpecToOpenAIFunctions } from 'openapi-to-functions';

const functionsFromUrl = convertRawOpenAPISpecToOpenAIFunctions('https://url.com/openapi.yml');
// or
const functionsFromSpec = convertRawOpenAPISpecToOpenAIFunctions(openApiSpecString);

Example

Input:

openapi: 3.1.0
info:
  title: Shop API
  version: 1.0.0
servers:
  - url: 'https://shop.com/api/v1'
paths:
  /order:
    get:
      summary: Retrieve an order by the provided order name
      parameters:
        - in: query
          name: orderName
          required: true
          schema:
            type: string
          description: Order name

outputs:

[
  {
    name: 'get_order',
    description: 'Retrieve an order by the provided order name',
    parameters: {
      type: 'object',
      properties: {
        orderName: {
          type: 'string',
          description: 'Order name',
          location: 'query',
        },
      },
      required: ['orderName'],
    },
  },
];

Then you can manipulate it further to get to a list of tools:

const tools = functionsFromSpec.map((func) => ({
  type: 'function',
  function: func,
}));

and use in OpenAI call:

const response = await openai.chat.completions.create({
  model: 'gpt-4o',
  messages: messages,
  tools: [
    {
      type: 'function',
      function: {
        name: 'get_order',
        description: 'Retrieve an order by the provided order name',
        parameters: {
          type: 'object',
          properties: {
            orderName: {
              type: 'string',
              description: 'Order name',
              location: 'query',
            },
          },
          required: ['orderName'],
        },
      },
    },
  ],
  tool_choice: 'auto',
});