Custom Extensions

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Custom Extensions Overview

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What Are Custom Extensions?

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Model Context Protocol (MCP)

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What is MCP?

• Standardized communication between AI and external systems
• Reusable server implementations
• Secure, controlled access to resources
• Community-driven ecosystem of integrations

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MCP Architecture

┌─────────────┐         ┌─────────────┐         ┌──────────────┐
│  ZeroTwo    │ ◄─MCP──►│ MCP Server  │ ◄──────►│ Data Source  │
│  (Client)   │         │             │         │ (API/DB/etc) │
└─────────────┘         └─────────────┘         └──────────────┘

• Client: ZeroTwo (requests resources/tools)
• Server: MCP server (provides capabilities)
• Resources: Data, files, system access

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Built-in MCP Servers

Show me the recent commits in the main branch of my project

Create a Linear issue for the authentication bug we discussed

Search my Notion workspace for documentation about the API

Show me the users table schema from my Supabase project

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Adding Custom MCP Servers

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Using Public MCP Servers

{
  "name": "weather-server",
  "url": "https://mcp.weather-api.com",
  "auth": "bearer",
  "token": "your-api-key"
}

What's the weather forecast for San Francisco this week?

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Self-Hosted MCP Servers

npm install -g @modelcontextprotocol/server-example

mcp-server start --port 3000

ngrok http 3000

# Deploy MCP server
vercel deploy

# Get deployment URL
https://your-mcp-server.vercel.app

FROM node:18-alpine

WORKDIR /app
COPY package*.json ./
RUN npm install
COPY . .

EXPOSE 3000
CMD ["npm", "start"]

# Build and run
docker build -t my-mcp-server .
docker run -p 3000:3000 my-mcp-server

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Creating Custom MCP Servers

npm init -y
npm install @modelcontextprotocol/sdk express

const { MCPServer } = require('@modelcontextprotocol/sdk');
const express = require('express');

const app = express();
const server = new MCPServer({
  name: 'my-custom-server',
  version: '1.0.0'
});

// Define a custom tool
server.addTool({
  name: 'get-user-data',
  description: 'Fetch user data from internal database',
  parameters: {
    type: 'object',
    properties: {
      userId: {
        type: 'string',
        description: 'User ID to fetch'
      }
    },
    required: ['userId']
  },
  handler: async ({ userId }) => {
    // Your custom logic here
    const userData = await fetchFromDatabase(userId);
    return {
      success: true,
      data: userData
    };
  }
});

// Mount MCP server
app.use('/mcp', server.middleware());

app.listen(3000, () => {
  console.log('MCP server running on port 3000');
});

// Provide access to resources
server.addResource({
  uri: 'db://users',
  name: 'User Database',
  description: 'Access to user records',
  mimeType: 'application/json',
  handler: async () => {
    const users = await getAllUsers();
    return JSON.stringify(users);
  }
});

server.setAuthHandler(async (token) => {
  // Validate API key
  const isValid = await validateToken(token);
  return isValid;
});

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Custom API Tools

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Simple API Tool

POST https://api.yourcompany.com/zerotwo-tools

{
  "tool": "get_inventory",
  "parameters": {
    "product_id": "12345"
  }
}

{
  "success": true,
  "data": {
    "product": "Widget",
    "quantity": 150,
    "location": "Warehouse A"
  }
}

{
  "type": "object",
  "properties": {
    "product_id": {
      "type": "string",
      "description": "Product SKU or ID"
    }
  },
  "required": ["product_id"]
}

Input: { "product_id": "12345" }
Expected: Successful inventory data retrieval

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Advanced Tool Configuration

{
  "Authorization": "Bearer ${API_KEY}",
  "Content-Type": "application/json",
  "X-Custom-Header": "value"
}

{
  "format": "json",
  "version": "2"
}

{
  "success": "$.status",
  "data": "$.result.data",
  "message": "$.result.message"
}

{
  "error_path": "$.error",
  "retry_on": [429, 503],
  "max_retries": 3
}

{
  "rate_limit": {
    "requests_per_minute": 60,
    "requests_per_hour": 1000,
    "burst": 10
  }
}

{
  "cache": {
    "enabled": true,
    "ttl": 300,
    "key": "product_${product_id}"
  }
}

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Database Connections (Enterprise)

{
  "type": "postgresql",
  "host": "db.yourcompany.com",
  "port": 5432,
  "database": "production",
  "username": "readonly_user",
  "password": "${DB_PASSWORD}",
  "ssl": true
}

{
  "type": "mongodb",
  "connection_string": "mongodb+srv://...",
  "database": "app_data",
  "collections": ["users", "products"],
  "read_only": true
}

{
  "type": "snowflake",
  "account": "xy12345",
  "warehouse": "COMPUTE_WH",
  "database": "ANALYTICS",
  "schema": "PUBLIC",
  "role": "READONLY"
}

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Extension Marketplace

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Finding Extensions

• ZeroTwo Extension Marketplace (built-in)
• GitHub MCP Server Registry
• NPM packages
• Community forums

• 📊 Data & Analytics
• 🔧 Development Tools
• 🤝 CRM & Sales
• 📝 Productivity
• 🎨 Creative Tools
• 🔐 Security & Compliance

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Installing from Marketplace

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Managing Extensions

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Extension Settings

• ✅ Enable/disable
• ⚙️ Configuration
• 🔐 Permissions
• 📊 Usage statistics
• 🔄 Update status
• 🗑️ Uninstall

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Permissions Management

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Updating Extensions

• Extensions update automatically
• Security patches applied immediately
• Breaking changes delayed with notice

1. Settings > Extensions
2. See “Update Available” badge
3. Review changelog
4. Click Update

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Best Practices

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Troubleshooting

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Next Steps