query
Run a read-only SQL query
LABSCO SUMMARY
The whole surface is one read-only query, which is both the point and the limit.
There is a single tool, query, taking a sql string, and the description says read-only and stops there. Anything a client might otherwise reach through a typed helper — which tables exist, what a column holds, how large a result will be — has to be written as SQL and sent through that same call, so the model's SQL is the interface. The trade reads cleanly in both directions: nothing here can write, and nothing here will describe the schema for you either.
What it is
A single-tool PostgreSQL server: query takes a sql string and runs it read-only against the database named in the connection string the server was started with.
What you get
- query runs a read-only SQL statement and returns its result; the sql string is the entire input.
- The target database is fixed by the connection string given at startup, so a running session cannot be pointed at a different database part-way through a conversation.
- Schema discovery goes through the same call: with query as the only entry point, finding out which tables exist is itself SQL.
Requirements
A PostgreSQL database you can reach and its connection string; the server itself takes no separate credentials.
Setup effort
One command — docker run -i --rm mcp/postgres postgresql://host.docker.internal:5432/mydb
USE CASES
01
Answering a data question without opening a client
Write the SQL, send it, read the rows back — the connection is already fixed to one database and nothing here can write to it.
1 tool
Counted once with only startup setup. Other versions, modes or optional credentials may expose a different list.
BEFORE YOU INSTALL
What to know first
Tools you get
1 tool when we connected.
Requires
docker on PATH
CONTEXT COST
Light Standing cost
Rated by the size of the one tool definition that rides along on every turn
INSTALLATION
Connect your client
Add the block to your client, or run the command directly.
Server setup
Configuration file
JSON
{
"mcpServers": {
"postgres": {
"command": "docker",
"args": [
"run",
"-i",
"--rm",
"mcp/postgres",
"postgresql://host.docker.internal:5432/mydb"
]
}
}
}docker
TERMINAL
docker run -i --rm mcp/postgres postgresql://host.docker.internal:5432/mydb
