Tools based on OpenAPI Spec

Last updated Apr 21, 2026 Oftentimes APIs are defined and documented via OpenAPI 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 Spects

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>;

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Tools based on OpenAPI Spec - 图1Docs

{"@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","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/workers-ai/features/function-calling/embedded/examples/openapi/og.png?v=d57cb6344a7eb170","dateModified":"2026-04-21","publisher":{"@type":"Organization","name":"Cloudflare","description":"One platform for your apps, agents, and workforce. Build, secure, and scale without managing infrastructure","url":"https://www.cloudflare.com/","sameAs":["https://github.com/cloudflare","https://www.linkedin.com/company/cloudflare","https://x.com/cloudflare"],"logo":{"@type":"ImageObject","url":"https://developers.cloudflare.com/logo.svg"},"address":{"@type":"PostalAddress","streetAddress":"101 Townsend St","addressLocality":"San Francisco","addressRegion":"CA","postalCode":"94107","addressCountry":"US"},"contactPoint":[{"@type":"ContactPoint","contactType":"Customer Support","url":"https://support.cloudflare.com/","availableLanguage":["English"]},{"@type":"ContactPoint","contactType":"Sales","url":"https://www.cloudflare.com/contact/","availableLanguage":["English"]}]},"isPartOf":{"@type":"WebSite","@id":"https://developers.cloudflare.com/#website","name":"Cloudflare Docs","url":"https://developers.cloudflare.com/"},"keywords":["AI"]}

description: Set up and deploy your first Workers AI project with embedded function calling. title: Get Started image: https://developers.cloudflare.com/workers-ai/features/function-calling/embedded/get-started/og.png?v=8085b109897093fc

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