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

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Install from npm:

``bash
npm install questdbmcp
`

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

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1. Clone this repository or navigate to the project directory:
`bash
cd questdbmcp
`

2. Install dependencies:
`bash
npm install
`

3. Build the project:
`bash
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:

$3

Run the MCP server directly:

`bash
npm start
`

Or for development:

`bash
npm run dev
`

Or install globally:

`bash
npm install -g questdbmcp
questdbmcp
`

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Install as a dependency in your TypeScript project:

`bash
npm install questdbmcp
`

#### Basic Usage

`typescript
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

`typescript
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

`typescript
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

`typescript
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

`typescript
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

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

#### TypeScript Types

All types are exported and available for use:

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

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#### 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:
`json
{
"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:
`json
{
"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:
`json
{
"table": "trades"
}
`

QuestDB Setup

$3

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

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`bash
brew install questdb
`

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

Development

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`bash
npm run build
`

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`bash
npm run typecheck
`

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`bash
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

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

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

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

License

MIT

Resources

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