QuestDB MCP Server

A Model Context Protocol (MCP) server for QuestDB that enables AI assistants to interact with QuestDB databases through tools for querying and inserting data.

Features

• Query Execution: Execute SELECT queries on QuestDB tables with structured output
• Data Insertion: Insert data into QuestDB tables using the InfluxDB Line Protocol
• Table Management: List tables and describe table schemas
• Automatic Schema Creation: Tables and columns are created automatically on insert
• Type Safety: Full TypeScript support with Zod schema validation
• Structured Output: All tools return structured content with output schemas
• MCP Logging: Integrated MCP logging messages for better observability
• Error Handling: Comprehensive error handling with graceful degradation
• Server Instructions: Built-in server instructions for AI assistants
• Graceful Shutdown: Proper cleanup on SIGINT/SIGTERM signals

Prerequisites

• Node.js v16 or newer
• QuestDB instance running (see QuestDB Quick Start)

Installation

As a Package

Install from npm:

npm install questdbmcp

Note: This package is publicly available on npm. No authentication or configuration is required to install or use it.

From Source

1. Clone this repository or navigate to the project directory:

   cd questdbmcp

2. Install dependencies:

   npm install

3. Build the project:

   npm run build

Configuration

The server can be configured using environment variables:

• QUESTDB_HOST - QuestDB host (default: localhost)
• QUESTDB_PORT - QuestDB port (default: 9000)
• QUESTDB_USERNAME - QuestDB username (optional, for authentication)
• QUESTDB_PASSWORD - QuestDB password (optional, for authentication)
• QUESTDB_AUTO_FLUSH_ROWS - Auto-flush after N rows (optional)
• QUESTDB_AUTO_FLUSH_INTERVAL - Auto-flush interval in milliseconds (optional)

Usage

This package can be used in two ways:

1. CLI Usage

Run the MCP server directly:

npm start

Or for development:

npm run dev

Or install globally:

npm install -g questdbmcp
questdbmcp

2. Library Usage

Install as a dependency in your TypeScript project:

npm install questdbmcp

Basic Usage

import { QuestDBMCPServer, loadConfig } from 'questdbmcp';

// Load configuration from environment variables
const config = loadConfig();

// Create server instance
const server = new QuestDBMCPServer(config);

// Start the server
await server.run();

Custom Configuration

import { QuestDBMCPServer, QuestDBConfig } from 'questdbmcp';

const config: QuestDBConfig = {
  host: 'localhost',
  port: 9000,
  username: 'admin',
  password: 'quest',
};

const server = new QuestDBMCPServer(config, {
  setupProcessHandlers: false, // Don't set up process handlers when using as library
  serverName: 'my-questdb-server',
  serverVersion: '1.0.0',
  instructions: 'Custom server instructions...',
});

await server.run();

Using with Custom Transport

import { QuestDBMCPServer, QuestDBConfig } from 'questdbmcp';
import { StreamableHTTPServerTransport } from '@modelcontextprotocol/sdk/server/streamableHttp.js';
import express from 'express';

const config: QuestDBConfig = {
  host: 'localhost',
  port: 9000,
};

const server = new QuestDBMCPServer(config, {
  setupProcessHandlers: false,
});

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

app.post('/mcp', async (req, res) => {
  const transport = new StreamableHTTPServerTransport({
    sessionIdGenerator: undefined,
    enableJsonResponse: true,
  });

  res.on('close', () => {
    transport.close();
  });

  await server.server.connect(transport);
  await transport.handleRequest(req, res, req.body);
});

app.listen(3000, () => {
  console.log('MCP server running on http://localhost:3000/mcp');
});

Accessing Internal Components

import { QuestDBMCPServer } from 'questdbmcp';

const server = new QuestDBMCPServer(config);

// Access the underlying MCP server
const mcpServer = server.server;

// Access the QuestDB client
const client = server.questDBClient;

// Access the logger
const logger = server.log;

// Use the client directly
const tables = await client.listTables();
const result = await client.query('SELECT * FROM my_table LIMIT 10');

// Use the logger
await logger.info('Custom log message', { metadata: 'value' });

Creating Custom Tools

import { QuestDBMCPServer, QuestDBConfig } from 'questdbmcp';
import { z } from 'zod';

const config: QuestDBConfig = {
  host: 'localhost',
  port: 9000,
};

const server = new QuestDBMCPServer(config, {
  setupProcessHandlers: false,
});

// Access the underlying MCP server to register custom tools
server.server.registerTool(
  'my-custom-tool',
  {
    title: 'My Custom Tool',
    description: 'A custom tool that uses QuestDB',
    inputSchema: {
      param: z.string().describe('A parameter'),
    },
  },
  async ({ param }) => {
    // Use the QuestDB client
    const client = server.questDBClient;
    const result = await client.query(`SELECT * FROM my_table WHERE col = '${param}'`);
    
    return {
      content: [
        {
          type: 'text',
          text: JSON.stringify(result, null, 2),
        },
      ],
    };
  }
);

await server.run();

Shutdown

// Gracefully shutdown the server
await server.shutdown();

TypeScript Types

All types are exported and available for use:

import type {
  QuestDBConfig,
  QueryResult,
  QuestDBMCPServerOptions,
} from 'questdbmcp';

Available Tools

1. query

Execute a SQL SELECT query on QuestDB.

Parameters:

• query (string, required): The SQL query to execute (SELECT queries only)
• format (string, optional): Output format - json or csv (default: json)

Example:

{
  "query": "SELECT * FROM trades LIMIT 10",
  "format": "json"
}

2. insert

Insert data into a QuestDB table. Tables and columns are created automatically if they don't exist.

Parameters:

• table (string, required): The name of the table to insert into
• data (object, required): An object containing the data to insert
  • Keys are column names
  • Values are the data (strings, numbers, booleans)
  • Use timestamp key for explicit timestamp (milliseconds since epoch)
  • If timestamp is not provided, the current time is used

Example:

{
  "table": "trades",
  "data": {
    "symbol": "ETH-USD",
    "side": "sell",
    "price": 2615.54,
    "amount": 0.00044,
    "timestamp": 1699123456789
  }
}

3. list_tables

List all tables in the QuestDB database.

Parameters: None

4. describe_table

Get the schema of a specific table.

Parameters:

• table (string, required): The name of the table to describe

Example:

{
  "table": "trades"
}

QuestDB Setup

Quick Start with Docker

docker run \
  -p 9000:9000 -p 9009:9009 -p 8812:8812 -p 9003:9003 \
  questdb/questdb:9.1.1

Quick Start with Homebrew (macOS)

brew install questdb

The QuestDB Web Console will be available at: http://localhost:9000

Development

Building

npm run build

Type Checking

npm run typecheck

Development Mode

npm run dev

Data Types

The insert tool automatically maps JavaScript types to QuestDB types:

• String → SYMBOL (indexed string type)
• Number (integer) → LONG
• Number (float) → DOUBLE
• Boolean → BOOLEAN
• Timestamp → TIMESTAMP (when using the timestamp field)

Security Notes

• Only SELECT queries are allowed through the query tool for safety
• The server uses the QuestDB REST API for queries and the InfluxDB Line Protocol for inserts
• Authentication is supported via username/password if your QuestDB instance requires it

Examples

Inserting Trade Data

{
  "tool": "insert",
  "arguments": {
    "table": "trades",
    "data": {
      "symbol": "BTC-USD",
      "side": "buy",
      "price": 39269.98,
      "amount": 0.001
    }
  }
}

Querying Data

{
  "tool": "query",
  "arguments": {
    "query": "SELECT symbol, price, amount FROM trades WHERE symbol = 'BTC-USD' ORDER BY timestamp DESC LIMIT 10"
  }
}

Listing Tables

{
  "tool": "list_tables",
  "arguments": {}
}

License

MIT

Resources

• QuestDB Documentation
• QuestDB Node.js Client
• Model Context Protocol