--- title: OpenAI Responses Tool Calling with AI Gateway product: vercel url: /docs/ai-gateway/sdks-and-apis/responses/tool-calling canonical_url: "https://vercel.com/docs/ai-gateway/sdks-and-apis/responses/tool-calling" last_updated: 2026-09-08 type: reference prerequisites: - /docs/ai-gateway/sdks-and-apis/responses - /docs/ai-gateway/sdks-and-apis related: [] summary: Define tools the model can call with the OpenAI Responses API through AI Gateway. install_vercel_plugin: npx plugins add vercel/vercel-plugin --- # OpenAI Responses Tool Calling with AI Gateway Define tools with JSON Schema parameters. The model can call them, and you can feed the results back in a follow-up request: ## Related pages > **For AI agents:** Follow these links to understand how this page connects to the rest of the Vercel ecosystem. For the full cross-link map (inbound, outbound, prerequisites, and semantic neighbors), see the .graph.md link below. - [OpenResponses Tool Calling with AI Gateway](https://vercel.com/docs/ai-gateway/sdks-and-apis/openresponses/tool-calling?from=related&source_path=%2Fdocs%2Fai-gateway%2Fsdks-and-apis%2Fresponses%2Ftool-calling&source_site=vercel-docs&relationship=related) — Define tools the model can call using the OpenResponses API through AI Gateway. - [Tools](https://ai-sdk.dev/docs/foundations/tools?from=related&source_path=%2Fdocs%2Fai-gateway%2Fsdks-and-apis%2Fresponses%2Ftool-calling&source_site=vercel-docs&relationship=related) - [OpenAI Chat Completions Tool Calling with AI Gateway](https://vercel.com/docs/ai-gateway/sdks-and-apis/openai-chat-completions/tool-calling?from=related&source_path=%2Fdocs%2Fai-gateway%2Fsdks-and-apis%2Fresponses%2Ftool-calling&source_site=vercel-docs&relationship=related) — Use function calling with the Chat Completions API to enable models to call tools and functions through AI Gateway. - [Anthropic Messages Tool Calling with AI Gateway](https://vercel.com/docs/ai-gateway/sdks-and-apis/anthropic-messages-api/tool-calling?from=related&source_path=%2Fdocs%2Fai-gateway%2Fsdks-and-apis%2Fresponses%2Ftool-calling&source_site=vercel-docs&relationship=related) — Use function calling with the Anthropic Messages API to allow models to call tools and functions through AI Gateway. - [OpenResponses API with AI Gateway](https://vercel.com/docs/ai-gateway/sdks-and-apis/openresponses?from=related&source_path=%2Fdocs%2Fai-gateway%2Fsdks-and-apis%2Fresponses%2Ftool-calling&source_site=vercel-docs&relationship=related) — Use the OpenResponses API specification with AI Gateway for a unified, provider-agnostic interface. - [OpenResponses Structured Outputs with AI Gateway](https://vercel.com/docs/ai-gateway/sdks-and-apis/openresponses/structured-outputs?from=related&source_path=%2Fdocs%2Fai-gateway%2Fsdks-and-apis%2Fresponses%2Ftool-calling&source_site=vercel-docs&relationship=related) — Constrain OpenResponses API output to a JSON schema so every response parses through AI Gateway. Full cross-link map for this page: [/docs/ai-gateway/sdks-and-apis/responses/tool-calling.graph.md](/docs/ai-gateway/sdks-and-apis/responses/tool-calling.graph.md?from=related&source_path=%2Fdocs%2Fai-gateway%2Fsdks-and-apis%2Fresponses%2Ftool-calling&source_site=vercel-docs&relationship=graph) #### TypeScript ```typescript filename="tools.ts" import OpenAI from 'openai'; const client = new OpenAI({ apiKey: process.env.AI_GATEWAY_API_KEY, baseURL: 'https://ai-gateway.vercel.sh/v1', }); const response = await client.responses.create({ model: 'openai/gpt-6-astra', input: 'What is the weather in San Francisco?', tools: [ { type: 'function', name: 'get_weather', description: 'Get the current weather for a location', strict: true, parameters: { type: 'object', properties: { location: { type: 'string' }, }, required: ['location'], additionalProperties: false, }, }, ], }); // The model returns function_call items in the output for (const item of response.output) { if (item.type === 'function_call') { console.log(`Call: ${item.name}(${item.arguments})`); } } ``` #### Python ```python filename="tools.py" import os import json from openai import OpenAI client = OpenAI( api_key=os.getenv('AI_GATEWAY_API_KEY'), base_url='https://ai-gateway.vercel.sh/v1', ) response = client.responses.create( model='openai/gpt-6-astra', input='What is the weather in San Francisco?', tools=[ { 'type': 'function', 'name': 'get_weather', 'description': 'Get the current weather for a location', 'strict': True, 'parameters': { 'type': 'object', 'properties': { 'location': {'type': 'string'}, }, 'required': ['location'], 'additionalProperties': False, }, }, ], ) for item in response.output: if item.type == 'function_call': print(f'Call: {item.name}({item.arguments})') ``` #### cURL ```bash filename="tool-calls.sh" curl -X POST "https://ai-gateway.vercel.sh/v1/responses" \ -H "Authorization: Bearer $AI_GATEWAY_API_KEY" \ -H "Content-Type: application/json" \ -d '{ "model": "openai/gpt-6-astra", "input": "What is the weather in San Francisco?", "tools": [ { "type": "function", "name": "get_weather", "description": "Get the current weather for a location", "strict": true, "parameters": { "type": "object", "properties": { "location": { "type": "string" } }, "required": [ "location" ], "additionalProperties": false } } ] }' ``` To continue the conversation with tool results, include the function call and its output in the next request's `input` array: #### TypeScript ```typescript const functionCall = response.output.find( (item) => item.type === 'function_call', ); const followup = await client.responses.create({ model: 'openai/gpt-6-astra', input: [ { role: 'user', content: 'What is the weather in San Francisco?' }, { type: 'function_call', id: functionCall.id, call_id: functionCall.call_id, name: functionCall.name, arguments: functionCall.arguments, }, { type: 'function_call_output', call_id: functionCall.call_id, output: JSON.stringify({ temperature: 68, condition: 'Sunny' }), }, ], tools: [ /* same tools as above */ ], }); console.log(followup.output_text); ``` #### Python ```python import json function_call = next( item for item in response.output if item.type == 'function_call' ) followup = client.responses.create( model='openai/gpt-6-astra', input=[ {'role': 'user', 'content': 'What is the weather in San Francisco?'}, { 'type': 'function_call', 'id': function_call.id, 'call_id': function_call.call_id, 'name': function_call.name, 'arguments': function_call.arguments, }, { 'type': 'function_call_output', 'call_id': function_call.call_id, 'output': json.dumps({'temperature': 68, 'condition': 'Sunny'}), }, ], tools=[ # same tools as above ], ) print(followup.output_text) ``` #### cURL ```bash filename="tool-followup.sh" curl -X POST "https://ai-gateway.vercel.sh/v1/responses" \ -H "Authorization: Bearer $AI_GATEWAY_API_KEY" \ -H "Content-Type: application/json" \ -d '{ "model": "openai/gpt-6-astra", "input": [ { "role": "user", "content": "What is the weather in San Francisco?" }, { "type": "function_call", "call_id": "call_abc123", "name": "get_weather", "arguments": "{\"location\": \"San Francisco, CA\"}" }, { "type": "function_call_output", "call_id": "call_abc123", "output": "{\"temperature\": 68, \"condition\": \"Sunny\"}" } ], "tools": [ { "type": "function", "name": "get_weather", "description": "Get the current weather for a location", "parameters": { "type": "object", "properties": { "location": { "type": "string" } }, "required": ["location"] } } ] }' ``` --- [View full sitemap](/docs/sitemap)