DuckDB / MotherDuck Local MCP Server

SQL analytics and data engineering for AI Assistants and IDEs.

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-write supported	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 or ~/.codex/config.toml -

Gemini CLI Use CLI commands below or ~/.gemini/settings.json -

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

Gemini CLI commands

In-Memory DuckDB (Dev Mode):

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

Local DuckDB (Read-Only):

gemini mcp add -s user duckdb uvx mcp-server-motherduck --db-path /absolute/path/to/db.duckdb

MotherDuck (Read-Write):

gemini mcp add -s user -e motherduck_token=YOUR_TOKEN motherduck 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-write capable, 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
`--motherduck-connection-parameters`	`session_hint=mcp&` `dbinstance_inactivity_ttl=0s`	Additional MotherDuck connection string parameters (`key=value` pairs separated by `&`)
`--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
`AWS_ENDPOINT`	AWS endpoint 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

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

Run the Release New Version GitHub Action
Enter version in MAJOR.MINOR.PATCH format
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

Release History

Version	Changes	Urgency	Date
v1.0.4	## What's Changed * Feat/s3 endpoint by @th1460 in https://github.com/motherduckdb/mcp-server-motherduck/pull/71 ## New Contributors * @th1460 made their first contribution in https://github.com/motherduckdb/mcp-server-motherduck/pull/71 Full Changelog: https://github.com/motherduckdb/mcp-server-motherduck/compare/v1.0.3...v1.0.4	Medium	3/30/2026
v1.0.3	## What's Changed * defer connection intialization to first tool call by @tdoehmen in https://github.com/motherduckdb/mcp-server-motherduck/pull/64 Full Changelog: https://github.com/motherduckdb/mcp-server-motherduck/compare/v1.0.2...v1.0.3	Low	3/4/2026
v1.0.2	## What's Changed * Add Codex CLI install instructions to README by @leonardovida in https://github.com/motherduckdb/mcp-server-motherduck/pull/58 * Add --scope user to Claude Code MCP examples by @leonardovida in https://github.com/motherduckdb/mcp-server-motherduck/pull/59 * Remote mcp supports rw by @mehd-io in https://github.com/motherduckdb/mcp-server-motherduck/pull/60 * add connections parameters, use fetchall() instead of fetchone by @tdoehmen in https://github.com/motherduckdb/mcp-serve	Low	3/3/2026
v1.0.1	## What's Changed * Add --stateless-http option for HTTP transport by @ken5scal in https://github.com/motherduckdb/mcp-server-motherduck/pull/56 ## New Contributors * @ken5scal made their first contribution in https://github.com/motherduckdb/mcp-server-motherduck/pull/56 Full Changelog: https://github.com/motherduckdb/mcp-server-motherduck/compare/v1.0.0...v1.0.1	Low	2/12/2026
v1.0.0	Full Changelog: https://github.com/motherduckdb/mcp-server-motherduck/compare/0.8.1...v1.0.0	Low	2/2/2026

Dependencies & License Audit

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mcp-server-motherduck

Description

README

DuckDB / MotherDuck Local MCP Server

Remote vs Local MCP

Quick Start

Connecting to In-Memory DuckDB (Dev Mode)

Connecting to a Local DuckDB File in Read-Only Mode

Connecting to MotherDuck in Read-Write Mode

Client Setup

Tools

Securing for Production

Command Line Parameters

Environment Variables

Troubleshooting

Resources

Development

Release Process

License

Release History

Dependencies & License Audit

Similar Packages