genkitx-mcp plugin with standalone MCP server

[asif166037]

I have created standalone MCP server now for connecting the MCP server I am using genkit MCP-plugin. for transport layer I am using StreamableHTTPClientTransport and sucessfully connected with it but how to pass the headers at the runtime.

Code -

import { z, genkit } from 'genkit';
import { googleAI } from '@genkit-ai/googleai';
import { mcpClient } from 'genkitx-mcp';
import { vertexAI } from '@genkit-ai/vertexai';
import { StreamableHTTPClientTransport } from '@modelcontextprotocol/sdk/client/streamableHttp.js';

const express = require('express');
const cors = require('cors');
require('dotenv').config();

const app = express();
app.use(express.json());

const createMCPClient = (accessToken: string) => {
const customTransport = new StreamableHTTPClientTransport(
new URL('http://localhost:3001/mcp'), // MCP server endpoint
{
requestInit: {
headers: { Authorization: ${accessToken} },
},
}
);

return mcpClient({
name: 'google-slides',
transport: customTransport,
});
};

const ai = genkit({
plugins: [
// vertexAI({
// location: 'europe-central2',
// projectId: 'global-bog-staging',
// }),
googleAI({ apiKey: '' }),
createMCPClient('')
],

model: googleAI.model('gemini-2.0-flash'),
});

const chat = async (req: any, res: any) => {
try {
let { message, userId, accessToken } = req.body;

const slideClient = createMCPClient(accessToken);


const contentResponse: any = await ai.generate({
  prompt: `User Request: ${message}.`,

  tools: ['google-slides/create_presentation'], // this is form MCP server
});

let result = contentResponse.message.content;
console.log(contentResponse.text);
// console.log(contentResponse.message.content);

return res.json({
  success: true,
  message: 'Presentation created successfully!! 🎉',
  chatResponse: result,
  userId,
  timestamp: new Date().toISOString(),
});

} catch (error: any) {
console.log('error', error);
res.status(500).json(error.Error);
}
};

app.post('/chat', chat);

app.listen(3000, () => {
console.log('Express APP running');
});

End goal - pass the access-token to the MCP server via http
Temporary solution -

1. Every API call I can create the genkit instance add pass the accesstoken in that, but it will create genkit instance every time and discovery the tool .
2. passing the access token via prompt