Execute a read-only SQL query against the PostgreSQL database. Args: query: The SQL query to execute (must be read-only) conn_id: Connection ID previously obtained from the connect tool params: Parameters for the query (optional) Returns: Query results as a list of dictionaries
AI agents call pg_query to retrieve information from Pg without modifying anything — typically the context-gathering step in research, monitoring, and reporting workflows, before the agent takes action elsewhere.
pg_query is restricted to read-only operations against a PostgreSQL database. It retrieves and returns data without creating, modifying, or deleting any records. The explicit read-only constraint and parameter validation in the description confirm this tool cannot perform writes, destructive operations, or execute arbitrary code.
From the tool's definition Tool description explicitly states 'Execute a read-only SQL query' and 'must be read-only'. The tool only returns query results as dictionaries with no data modification capability.
Documented attack patterns abuse exactly the kind of access pg_query gives an agent:
PolicyLayer is an MCP gateway — it sits between your AI agents and Pg, and nothing reaches the server without passing your rules. This is the rule we recommend for pg_query:
{
"version": "1",
"default": "deny",
"tools": {
"pg_query": {}
}
}pg_query is read-only, so it stays allowed — but everything else on the server is denied unless you say otherwise.
Free to start. No card required.
Execute a read-only SQL query against the PostgreSQL database. Args: query: The SQL query to execute (must be read-only) conn_id: Connection ID previously obtained from the connect tool params: Parameters for the query (optional) Returns: Query results as a list of dictionaries. It is categorised as a Read tool in the Pg MCP Server, which means it retrieves data without modifying state.
Register the Pg MCP server in PolicyLayer and add a rule for pg_query: allow, deny, rate-limit, or require approval. Point your MCP client at the PolicyLayer proxy URL and the rule is enforced on every call, before it reaches Pg. Nothing to install.
pg_query is a Read tool with low risk. Read-only tools are generally safe to allow by default.
Yes. Add a rate_limit block to the pg_query rule in your PolicyLayer policy. For example, setting max: 10 and window: 60 limits the tool to 10 calls per minute. Rate limits are tracked per agent session and reset automatically.
Set action: deny in the PolicyLayer policy for pg_query. The AI agent will receive a policy violation error and cannot call the tool. You can also include a reason field to explain why the tool is blocked.
pg_query is provided by the Pg MCP server (stuzero/pg-mcp-server). PolicyLayer sits as a proxy in front of this server to enforce policies before tool calls reach the server.
Deterministic rules across all 5 Pg tools. Per-identity grants. Full audit log. Live in minutes. Nothing to install.
Free to start. No card required.
5 Pg tools catalogued and risk-classified — across an index of 42,500+ MCP servers.