DuckDB / MotherDuck Local MCP Server

SQL analytics and data engineering for AI Assistants and IDEs.

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Connect AI assistants to your data using DuckDB's powerful analytical SQL engine. Supports connecting to local DuckDB files, in-memory databases, S3-hosted databases, and MotherDuck. Allows executing SQL read- and write-queries, browsing database catalogs, and switching between different database connections on-the-fly.

Looking for a fully-managed remote MCP server for MotherDuck? → Go to the MotherDuck Remote MCP docs

Remote vs Local MCP

	Remote MCP	Local MCP (this repo)
Hosting	Hosted by MotherDuck	Runs locally/self-hosted
Setup	Zero-setup	Requires local installation
Access	Read-only	Read-write supported
Local filesystem	-	Query across local and remote databases, ingest data from / export data to local filesystem

📝 Migrating from v0.x?

• Read-only by default: The server now runs in read-only mode by default. Add --read-write to enable write access. See Securing for Production.
• Default database changed: --db-path default changed from md: to :memory:. Add --db-path md: explicitly for MotherDuck.
• MotherDuck read-only requires read-scaling token: MotherDuck connections in read-only mode require a read-scaling token. Regular tokens require --read-write.

Quick Start

Prerequisites: Install uv via pip install uv or brew install uv

Connecting to In-Memory DuckDB (Dev Mode)

{
  "mcpServers": {
    "DuckDB (in-memory, r/w)": {
      "command": "uvx",
      "args": ["mcp-server-motherduck", "--db-path", ":memory:", "--read-write", "--allow-switch-databases"]
    }
  }
}

Full flexibility with no guardrails — read-write access and the ability to switch to any database (local files, S3, or MotherDuck) at runtime.

Connecting to a Local DuckDB File in Read-Only Mode

{
  "mcpServers": {
    "DuckDB (read-only)": {
      "command": "uvx",
      "args": ["mcp-server-motherduck", "--db-path", "/absolute/path/to/your.duckdb"]
    }
  }
}

Connects to a specific DuckDB file in read-only mode. Won't hold on to the file lock, so convenient to use alongside a write connection to the same DuckDB file. You can also connect to remote DuckDB files on S3 using s3://bucket/path.duckdb — see Environment Variables for S3 authentication. If you're considering third-party access to the MCP, see Securing for Production.

Connecting to MotherDuck in Read-Write Mode

{
  "mcpServers": {
    "MotherDuck (local, r/w)": {
      "command": "uvx",
      "args": ["mcp-server-motherduck", "--db-path", "md:", "--read-write"],
      "env": {
        "motherduck_token": "<YOUR_MOTHERDUCK_TOKEN>"
      }
    }
  }
}

See Command Line Parameters for more options, Securing for Production for deployment guidance, and Troubleshooting if you encounter issues.

Client Setup

Client	Config Location	One-Click Install
Claude Desktop	Settings → Developer → Edit Config	.mcpb (MCP Bundle)
Claude Code	Use CLI commands below	-
Codex CLI	Use CLI commands below	-
Cursor	Settings → MCP → Add new global MCP server
VS Code	Ctrl+Shift+P → "Preferences: Open User Settings (JSON)"

Any MCP-compatible client can use this server. Add the JSON configuration from Quick Start to your client's MCP config file. Consult your client's documentation for the config file location.

Claude Code CLI commands

In-Memory DuckDB (Dev Mode):

claude mcp add --scope user duckdb --transport stdio -- uvx mcp-server-motherduck --db-path :memory: --read-write --allow-switch-databases

Local DuckDB (Read-Only):

claude mcp add --scope user duckdb --transport stdio -- uvx mcp-server-motherduck --db-path /absolute/path/to/db.duckdb

MotherDuck (Read-Write):

claude mcp add --scope user motherduck --transport stdio --env motherduck_token=YOUR_TOKEN -- uvx mcp-server-motherduck --db-path md: --read-write

Codex CLI commands

In-Memory DuckDB (Dev Mode):

codex mcp add duckdb -- uvx mcp-server-motherduck --db-path :memory: --read-write --allow-switch-databases

Local DuckDB (Read-Only):

codex mcp add duckdb -- uvx mcp-server-motherduck --db-path /absolute/path/to/db.duckdb

MotherDuck (Read-Write):

codex mcp add motherduck --env motherduck_token=YOUR_TOKEN -- uvx mcp-server-motherduck --db-path md: --read-write

Tools

Tool	Description	Required Inputs	Optional Inputs
execute_query	Execute SQL query (DuckDB dialect)	sql	-
list_databases	List all databases (useful for MotherDuck or multiple attached DBs)	-	-
list_tables	List tables and views	-	database, schema
list_columns	List columns of a table/view	table	database, schema
switch_database_connection*	Switch to different database	path	create_if_not_exists

*Requires --allow-switch-databases flag

All tools return JSON. Results are limited to 1024 rows / 50,000 chars by default (configurable via --max-rows, --max-chars).

Securing for Production

When giving third parties access to a self-hosted MCP server, read-only mode alone is not sufficient — it still allows access to the local filesystem, changing DuckDB settings, and other potentially sensitive operations.

For production deployments with third-party access, we recommend MotherDuck Remote MCP — zero-setup, read-only, and hosted by MotherDuck.

Self-hosting MotherDuck MCP: Fork this repo and customize as needed. Use a service account with read-scaling tokens and enable SaaS mode to restrict local file access.

Self-hosting DuckDB MCP: Use --init-sql to apply security settings. See the Securing DuckDB guide for available options.

Command Line Parameters

Parameter	Default	Description
--db-path	:memory:	Database path: local file (absolute), md: (MotherDuck), or s3:// URL
--motherduck-token	motherduck_token env var	MotherDuck access token
--read-write	False	Enable write access
--motherduck-saas-mode	False	MotherDuck SaaS mode (restricts local access)
--allow-switch-databases	False	Enable switch_database_connection tool
--max-rows	1024	Max rows returned
--max-chars	50000	Max characters returned
--query-timeout	-1	Query timeout in seconds (-1 = disabled)
--init-sql	None	SQL to execute on startup
--ephemeral-connections	True	Use temporary connections for read-only local files
--transport	stdio	Transport type: stdio or http
--stateless-http	False	For protocol compatibility only (e.g. with AWS Bedrock AgentCore Runtime). Server still maintains global state via the shared DatabaseClient.
--port	8000	Port for HTTP transport
--host	127.0.0.1	Host for HTTP transport

Environment Variables

Variable	Description
motherduck_token or MOTHERDUCK_TOKEN	MotherDuck access token (alternative to --motherduck-token)
HOME	Used by DuckDB for extensions and config. Override with --home-dir if not set.
AWS_ACCESS_KEY_ID	AWS access key for S3 database connections
AWS_SECRET_ACCESS_KEY	AWS secret key for S3 database connections
AWS_SESSION_TOKEN	AWS session token for temporary credentials (IAM roles, SSO, EC2 instance profiles)
AWS_DEFAULT_REGION	AWS region for S3 connections

Troubleshooting

• spawn uvx ENOENT: Specify full path to uvx (run which uvx to find it)
• File locked: Make sure --ephemeral-connections is turned on (default: true) and that you're not connected in read-write mode

Resources

• MotherDuck MCP Documentation
• Close the Loop: Faster Data Pipelines with MCP, DuckDB & AI (Blog)
• Faster Data Pipelines with MCP and DuckDB (YouTube)

Development

To run from source:

{
  "mcpServers": {
    "Local DuckDB (Dev)": {
      "command": "uv",
      "args": ["--directory", "/path/to/mcp-server-motherduck", "run", "mcp-server-motherduck", "--db-path", "md:"],
      "env": {
        "motherduck_token": "<YOUR_MOTHERDUCK_TOKEN>"
      }
    }
  }
}

Release Process

1. Run the Release New Version GitHub Action
2. Enter version in MAJOR.MINOR.PATCH format
3. The workflow bumps version, publishes to PyPI/MCP registry, and creates the GitHub release with MCPB package

License

MIT License - see LICENSE file.

mcp-name: io.github.motherduckdb/mcp-server-motherduck