usql-mcp

USQL MCP Server

usql-mcp bridges the Model Context Protocol with the usql CLI so assistants and other MCP clients can run queries against any database usql supports. The server forwards tool requests directly to usql and streams the raw CLI output back to the caller (JSON by default, CSV on request), keeping behaviour identical to what you would see on the command line.

Requirements

• Node.js 16 or newer
• npm
• usql installed and available on PATH

Quick Launch with npm exec

Once the package is published you will be able to run it directly via:

npx usql-mcp

Until it is published, you can still spin it up straight from the repository using npm’s Git support (the prepare script compiles the TypeScript automatically):

npx github:jvm/usql-mcp

Both commands download the package, build dist/, and execute the CLI entry point (usql-mcp), which runs the MCP server on stdio.

Getting Started

git clone https://github.com/yourusername/usql-mcp.git
cd usql-mcp
npm install
npm run build

The compiled files live in dist/. They are intentionally not committed—run npm run build whenever you need fresh output.

Configuring Connections

Define connection strings via environment variables (USQL_*) or a config.json file mirroring config.example.json. Each USQL_<NAME>=... entry becomes a reusable connection whose name is the lower-cased <name> portion (USQL_ORACLE1 → oracle1). Reserved keys that aren’t treated as connections are:

• USQL_CONFIG_PATH
• USQL_QUERY_TIMEOUT_MS
• USQL_DEFAULT_CONNECTION

Examples:

export USQL_POSTGRES="postgres://user:password@localhost:5432/mydb"
export USQL_SQLITE="sqlite:///$(pwd)/data/app.db"
export USQL_ORACLE1="oracle://user:secret@host1:1521/service"
export USQL_ORACLE2="oracle://user:secret@host2:1521/service"

You can also supply a full URI directly in tool requests. USQL_QUERY_TIMEOUT_MS controls the default query timeout; leave it unset (or set defaults.queryTimeout to null) for unlimited execution and override it when you need a guard. Individual tool calls can pass timeout_ms to override (set to null for unlimited on that call). Set USQL_DEFAULT_CONNECTION (or defaults.defaultConnection in config.json) to name the connection that should be used automatically when a tool call omits the connection_string field.

For Claude Desktop, point the MCP configuration to the compiled entry point:

{
  "mcpServers": {
    "usql": {
      "command": "node",
      "args": ["/absolute/path/to/usql-mcp/dist/index.js"]
    }
  }
}

Tool Catalogue

Tool	Purpose	Notable Inputs
execute_query	Run an arbitrary SQL statement	connection_string, query, optional output_format (json|csv), timeout_ms
execute_script	Execute a multi-statement script	connection_string, script, optional output_format, timeout_ms
list_databases	List databases available on the server	connection_string, optional output_format, timeout_ms
list_tables	List tables in the current database	connection_string, optional output_format, timeout_ms
describe_table	Inspect table metadata via \d	connection_string, table, optional output_format, timeout_ms

Successful calls return the exact stdout produced by usql, paired with the format indicator:

{
  "format": "json", // or "csv"
  "content": "[{\"id\":1}]"
}

If usql exits with a non-zero code the handler forwards the message through the MCP error shape, keeping details like the sanitized connection string and original stderr.

Development

• npm run dev – TypeScript compile in watch mode
• npm run build – emit ESM output to dist/
• npm run lint – ESLint/Prettier rules
• npm run test – Jest unit tests (no external services required)
• npm run type-check – strict tsc --noEmit

Debug logging follows the namespace in DEBUG=usql-mcp:*.

Contributing

See AGENTS.md for contributor guidelines. Open an issue before large changes so we can keep the tooling lean and aligned with the MCP ecosystem.