Execute a SQL query against the PostgreSQL database. This tool is READ-ONLY by default. Use the
AI agents call query to retrieve information from Postgres without modifying anything — typically the context-gathering step in research, monitoring, and reporting workflows, before the agent takes action elsewhere.
The tool is explicitly described as read-only by default, meaning it retrieves data without side effects. However, the phrase 'by default' implies read-only mode may be configurable, and the sibling tool 'execute' suggests this server supports write/execute operations separately. The medium severity reflects that even read-only SQL access can expose sensitive data across the entire database if misused.
From the tool's definition 'Execute a SQL query against the PostgreSQL database. This tool is READ-ONLY by default.'
Documented attack patterns abuse exactly the kind of access query gives an agent:
PolicyLayer is an MCP gateway — it sits between your AI agents and Postgres, and nothing reaches the server without passing your rules. This is the rule we recommend for query:
{
"version": "1",
"default": "deny",
"tools": {
"query": {}
}
}query is read-only, so it stays allowed — but everything else on the server is denied unless you say otherwise.
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Execute a SQL query against the PostgreSQL database. This tool is READ-ONLY by default. Use the. It is categorised as a Read tool in the Postgres MCP Server, which means it retrieves data without modifying state.
Register the Postgres 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 Postgres. 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 Postgres MCP server (javimaligno/postgres_mcp). PolicyLayer sits as a proxy in front of this server to enforce policies before tool calls reach the server.
Start from Postgres, add the rest of your stack, and see everything your agents can call. Then put policy on all of it.
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14 Postgres tools catalogued and risk-classified — across an index of 43,000+ MCP servers.