MCP-Style Server — Google Docs & Gmail Integration

A lightweight Python server that exposes Google Docs and Gmail operations as MCP-style tool endpoints via FastAPI. Every action requires explicit human approval in the terminal before execution.

Features

• Append to Google Doc — Append text content to any Google Doc you have access to.

• Create Gmail Draft — Create a draft email in your Gmail account.

• Human-in-the-Loop — Every action is printed to the terminal and requires y/n approval.

• OAuth 2.0 — Secure authentication via Google's OAuth 2.0 flow.

Related MCP server: Google MCP Server

Prerequisites

• Python 3.9+

• Google Cloud Project with the following APIs enabled:

  • Google Docs API

  • Gmail API

• OAuth 2.0 Client Credentials (credentials.json) downloaded from the Google Cloud Console.

Setup

1. Clone the repository

git clone <repo-url>
cd MCP_server

2. Create a virtual environment (recommended)

python -m venv venv
# Windows
venv\Scripts\activate
# macOS/Linux
source venv/bin/activate

3. Install dependencies

pip install -r requirements.txt

4. Add your credentials

Place your Google OAuth client secrets file in the project root. The server is pre-configured to look for the credentials file by its downloaded name. If you renamed it, update the CREDENTIALS_FILE path in auth.py.

5. Run the server

python server.py

On the first run, a browser window will open asking you to sign in and grant permissions. After approval, a token.json file is created and subsequent runs will not require browser login.

Usage

Append to a Google Doc

curl -X POST http://127.0.0.1:8000/append_to_doc \
  -H "Content-Type: application/json" \
  -d '{"doc_id": "YOUR_DOC_ID", "content": "Hello from MCP server!"}'

Check the terminal running the server — you'll see:

============================================================
  ACTION: append_to_doc
============================================================
{
  "doc_id": "YOUR_DOC_ID",
  "content": "Hello from MCP server!"
}
============================================================
Approve? (y/n):

Type y to approve and execute, or n to reject.

Create a Gmail Draft

curl -X POST http://127.0.0.1:8000/create_email_draft \
  -H "Content-Type: application/json" \
  -d '{"to": "recipient@example.com", "subject": "Test", "body": "Hello!"}'

API Reference

POST /append_to_doc

Response (200):

{ "status": "success", "message": "Content appended to document.", "doc_id": "..." }

POST /create_email_draft

Response (200):

{ "status": "success", "message": "Draft created successfully.", "draft_id": "..." }

Error Responses

Project Structure

MCP_server/
├── server.py          → FastAPI app with tool endpoints
├── auth.py            → Google OAuth 2.0 authentication
├── docs_tool.py       → Google Docs tool (append content)
├── gmail_tool.py      → Gmail tool (create draft)
├── requirements.txt   → Python dependencies
├── Procfile           → Railway deployment config
├── README.md          → This file
├── .gitignore         → Git ignore rules
└── docs/
    ├── problemStatement.md
    └── architecture.md

Deploy to Railway

Prerequisites

• A Railway account (free tier available)

• The project pushed to GitHub (see Setup above)

• Google OAuth token.json generated locally (run the server once locally first)

Step 1: Create a New Project on Railway

1. Go to railway.app and log in.

2. Click "New Project" → "Deploy from GitHub Repo".

3. Select your repository: nikhil1102-ai/custom_mcp_server.

4. Railway will auto-detect the Procfile and configure the start command.

Step 2: Configure Environment Variables

In your Railway project dashboard, go to Variables and add:

Note: Railway automatically sets the PORT variable — you do not need to add it manually.

Step 3: Set Up Google OAuth Token

Since Railway has no browser for the OAuth consent flow, you must generate token.json locally first:

1. Run the server locally once:

   python server.py

2. Make any API call (e.g., append to doc) — this triggers the OAuth browser flow.

3. Complete the consent in your browser — token.json is created.

4. Copy the token contents:

   # Windows (PowerShell)
   Get-Content token.json
   
   # macOS/Linux
   cat token.json

5. Paste the entire JSON into the GOOGLE_TOKEN_JSON Railway variable.

Alternative: You can also upload token.json and credentials.json as Railway volume mounts if your plan supports it.

Step 4: Handle Credentials in Production

For Railway, the credentials.json and token.json files need to be provided via environment variables since they can't be committed to git. Update auth.py to read from env vars by adding this pattern (optional enhancement):

import json
import os

# If GOOGLE_TOKEN_JSON env var is set, write it to token.json on startup
token_env = os.getenv("GOOGLE_TOKEN_JSON")
if token_env and not os.path.exists("token.json"):
    with open("token.json", "w") as f:
        f.write(token_env)

Step 5: Deploy

1. Push your code to GitHub:

   git add .
   git commit -m "Add Railway deployment support"
   git push origin main

2. Railway will auto-deploy from the main branch.

3. Once deployed, Railway provides a public URL like:

   https://your-app-name.up.railway.app

Step 6: Test the Deployed API

# Replace with your Railway URL
curl -X POST https://your-app-name.up.railway.app/append_to_doc \
  -H "Content-Type: application/json" \
  -d '{"doc_id": "YOUR_DOC_ID", "content": "Hello from Railway!"}'

curl -X POST https://your-app-name.up.railway.app/create_email_draft \
  -H "Content-Type: application/json" \
  -d '{"to": "test@example.com", "subject": "Test", "body": "Deployed!"}'

Railway Environment Summary

Security Notes

• credentials.json and token.json are excluded from version control via .gitignore.

• The server binds to 127.0.0.1 (localhost) by default — it is not exposed to the network.

• On Railway, set AUTO_APPROVE=true since there is no terminal for manual approval.

• Only documents and gmail.compose OAuth scopes are requested.

• For production, consider adding API key authentication to protect your endpoints.