This record as markdown: /tools/postgres/query.md
What query does on PostgreSQL
AI agents call query to retrieve information from PostgreSQL without modifying anything. It is typically the context-gathering step in research, monitoring, and reporting workflows, before the agent takes action elsewhere.
Why query is rated Low
A read-only SQL query tool can only retrieve or inspect data without side effects. Even though SQL queries can be complex, the read-only restriction prevents Write, Destructive, Execute, and Financial risks. Severity is low because the blast radius is limited to information disclosure; an agent cannot cause operational damage through this tool alone.
From the tool's definition Tool name is 'query' and description explicitly states 'Run a read-only SQL query'. The read-only constraint means no data modification, deletion, or execution of arbitrary code is possible.
Attacks that exploit this kind of access
The rule that runs query safely
PolicyLayer is an MCP gateway: it sits between your AI agents and PostgreSQL, and checks every tool call against a rule you set before the call runs. Nothing changes on the server itself. For query, this is the rule to start with:
query is read-only, so it stays allowed. Everything else on the server is denied unless you say otherwise.
The button opens the PolicyLayer dashboard: create your workspace, connect PostgreSQL, apply this rule, and every query call is checked against it from then on.
Questions about query
Run a read-only SQL query. It is categorised as a Read tool in the PostgreSQL MCP Server, which means it retrieves data without modifying state.
Register the PostgreSQL MCP server in PolicyLayer and add a rule for 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 PostgreSQL. Nothing to install.
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 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 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.
query is provided by the PostgreSQL MCP server (@modelcontextprotocol/server-postgres). PolicyLayer sits as a proxy in front of this server to enforce policies before tool calls reach the server.
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