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

> Documentation Index  
> Fetch the complete documentation index at: https://developers.cloudflare.com/workers-ai/llms.txt  
> Use this file to discover all available pages before exploring further. 

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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

```
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://developers.cloudflare.com/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://developers.cloudflare.com/workers-ai/features/function-calling/embedded/examples/openapi/","inLanguage":"en","image":"https://developers.cloudflare.com/dev-products-preview.png","dateModified":"2026-04-21","publisher":{"@type":"Organization","name":"Cloudflare","url":"https://www.cloudflare.com/"},"isPartOf":{"@type":"WebSite","@id":"https://developers.cloudflare.com/#website","name":"Cloudflare Docs","url":"https://developers.cloudflare.com/"},"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"}}]}
```