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Overview

This recipe shows how to wire Nexus MCP tools to the official OpenAI Node SDK using function calling.
Why manual function calling? The standard OpenAI SDK doesn’t have native MCP support yet. OpenAI announced MCP support for their Responses API is coming soon, but it’s not available in the openai package yet.Want a simpler approach? Check out the OpenAI Agents SDK recipe which has native MCP support via hostedMcpTool() - no manual tool looping required!

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Access Token Setup (Next.js)

Why Civic Auth? Nexus needs to identify which user is accessing tools and authorize their permissions. Civic Auth provides the secure access token. (Support for additional identity providers coming soon.)
  • 1. next.config.ts
  • 2. API Route
  • 3. Middleware
  • 4. Get Token
import { createCivicAuthPlugin } from "@civic/auth/nextjs"
import type { NextConfig } from "next";

const nextConfig: NextConfig = {};
const withCivicAuth = createCivicAuthPlugin({ clientId: "YOUR_CLIENT_ID" });
export default withCivicAuth(nextConfig)

Full Integration Guide

Complete Next.js setup with frontend components, configuration options, and deployment details

AI Prompt for Next.js

Use Claude, ChatGPT, or other AI assistants to automatically set up Civic Auth
Get your Client ID at auth.civic.com
Non-Next.js: Forward a Bearer token from your frontend or validate incoming tokens server-side (see /libraries/auth-verify).

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Create an MCP Client

import OpenAI from 'openai';
import { StreamableHTTPClientTransport } from '@modelcontextprotocol/sdk/client/streamableHttp.js';
import { Client } from '@modelcontextprotocol/sdk/client/index.js';
import { getTokens } from '@civic/auth/nextjs';

async function createMCP() {
  const { accessToken } = await getTokens();

  if (!accessToken) {
    throw new Error('No access token available. User must be authenticated.');
  }

  const transport = new StreamableHTTPClientTransport('https://nexus.civic.com/hub/mcp', {
    requestInit: { headers: { Authorization: `Bearer ${accessToken}`, 'Content-Type': 'application/json' } },
  });
  const client = new Client({ name: 'my-app', version: '1.0.0' }, { capabilities: {} });
  await client.connect(transport);
  return client;
}

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Call with Tool Functions

export async function chatWithTools(messages: any[]) {
  const openai = new OpenAI({ apiKey: process.env.OPENAI_API_KEY! });
  const mcp = await createMCP();
  const { tools } = await mcp.listTools();

  const toolDefs = tools.map((t) => ({
    type: 'function' as const,
    function: { name: t.name, description: t.description, parameters: t.inputSchema },
  }));

  let response = await openai.chat.completions.create({
    model: 'gpt-4o-mini',
    messages,
    tools: toolDefs,
    tool_choice: 'auto',
  });

  const call = response.choices[0]?.message?.tool_calls?.[0];
  if (call) {
    const toolName = call.function.name;
    const args = JSON.parse(call.function.arguments || '{}');
    const result = await mcp.callTool({ name: toolName, arguments: args });

    // Send tool result back to the model
    response = await openai.chat.completions.create({
      model: 'gpt-4o-mini',
      messages: [
        ...messages,
        response.choices[0].message,
        { role: 'tool', tool_call_id: call.id, content: JSON.stringify(result.content) },
      ],
    });
  }

  await mcp.close();
  return response;
}

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Notes

  • Obtain the Civic access token via your server environment (e.g., Next.js getTokens()), or forward a Bearer token from a trusted frontend.
  • To verify tokens server-side in non-Next.js stacks, see /libraries/auth-verify.
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