Hosted Tools | OpenUI - The Open Standard for Generative UI

The Responses API can run supported tools inside the Gateway. Application function tools remain in your backend so your authorization and business logic stay under application control.

Capability	Declaration	Runs in
Web search	`{ type: "web_search" }`	Gateway
Image search	`{ type: "image_search" }`	Gateway
Remote MCP	`{ type: "mcp", server_label, server_url }`	Gateway
Application function	`{ type: "function", name, parameters }`	Your backend

import { generateSystemPrompt } from "@openuidev/lang-core";
import type { Tool } from "openai/resources/responses/responses";
import library from "./openui.spec.json";

const response = await gateway.responses.create({
  model: "openai/gpt-5",
  input: "Research the market and summarize the most important changes.",
  instructions: generateSystemPrompt({ cloud: true, library }),
  tools: [
    { type: "web_search" },
    { type: "image_search" } as unknown as Tool,
    {
      type: "mcp",
      server_label: "deepwiki",
      server_url: "https://mcp.deepwiki.com/mcp",
    } as unknown as Tool,
  ],
  stream: true,
});

The casts are required while image search and MCP remain Gateway extensions to the OpenAI SDK's published tool union.

For a function tool, execute each returned function_call in your backend and continue the response with a matching function_call_output.