---
title: Tools based on OpenAPI Spec
description: Generate Workers AI function calling tools from an OpenAPI specification using the ai-utils package.
image: https://edgetunnel-b2h.pages.dev/dev-products-preview.png
---

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# Tools based on OpenAPI Spec

Oftentimes APIs are defined and documented via [OpenAPI specification ↗](https://swagger.io/specification/). The Cloudflare `ai-utils` package's `createToolsFromOpenAPISpec` function creates tools from the OpenAPI spec, which the LLM can then leverage to fulfill the prompt.

In this example the LLM will describe the a Github user, based Github's API and its OpenAPI spec.

**Embedded function calling example from OpenAPI Spec**

```ts
import { createToolsFromOpenAPISpec, runWithTools } from '@cloudflare/ai-utils';


type Env = {
  AI: Ai;
};


const APP_NAME = 'cf-fn-calling-example-app';


export default {
  async fetch(request, env, ctx) {
    const toolsFromOpenAPISpec = [
      // You can pass the OpenAPI spec link or contents directly
      ...(await createToolsFromOpenAPISpec(
        'https://gist.githubusercontent.com/mchenco/fd8f20c8f06d50af40b94b0671273dc1/raw/f9d4b5cd5944cc32d6b34cad0406d96fd3acaca6/partial_api.github.com.json',
        {
          overrides: [
            {
              matcher: ({ url }) => {
                return url.hostname === 'api.github.com';
              },
              // for all requests on *.github.com, we'll need to add a User-Agent.
              values: {
                headers: {
                  'User-Agent': APP_NAME,
                },
              },
            },
          ],
        }
      )),
    ];


    const response = await runWithTools(
      env.AI,
      '@hf/nousresearch/hermes-2-pro-mistral-7b',
      {
        messages: [
          {
            role: 'user',
            content: 'Who is cloudflare on Github and how many repos does the organization have?',
          },
        ],
        tools: toolsFromOpenAPISpec,
      }
    );


    return new Response(JSON.stringify(response));
  },
} satisfies ExportedHandler<Env>;
```

```json
{"@context":"https://schema.org","@type":"WebPage","@id":"https://edgetunnel-b2h.pages.dev/workers-ai/features/function-calling/embedded/examples/openapi/#page","headline":"Tools based on OpenAPI Spec · Cloudflare Workers AI docs","description":"Generate Workers AI function calling tools from an OpenAPI specification using the ai-utils package.","url":"https://edgetunnel-b2h.pages.dev/workers-ai/features/function-calling/embedded/examples/openapi/","inLanguage":"en","image":"https://edgetunnel-b2h.pages.dev/dev-products-preview.png","dateModified":"2026-04-21","publisher":{"@type":"Organization","name":"Cloudflare","url":"https://www.cloudflare.com/"},"isPartOf":{"@type":"WebSite","@id":"https://edgetunnel-b2h.pages.dev/#website","name":"Cloudflare Docs","url":"https://edgetunnel-b2h.pages.dev/"},"keywords":["AI"]}
{"@context":"https://schema.org","@type":"BreadcrumbList","itemListElement":[{"@type":"ListItem","position":1,"item":{"@id":"/directory/","name":"Directory"}},{"@type":"ListItem","position":2,"item":{"@id":"/workers-ai/","name":"Workers AI"}},{"@type":"ListItem","position":3,"item":{"@id":"/workers-ai/features/","name":"Features"}},{"@type":"ListItem","position":4,"item":{"@id":"/workers-ai/features/function-calling/","name":"Function calling"}},{"@type":"ListItem","position":5,"item":{"@id":"/workers-ai/features/function-calling/embedded/","name":"Embedded"}},{"@type":"ListItem","position":6,"item":{"@id":"/workers-ai/features/function-calling/embedded/examples/","name":"Examples"}},{"@type":"ListItem","position":7,"item":{"@id":"/workers-ai/features/function-calling/embedded/examples/openapi/","name":"Tools based on OpenAPI Spec"}}]}
```