Run a read-only SQL query against the PostgreSQL database and return the results as JSON. Use this tool to retrieve data without modifying the database. Only SELECT statements and other non-modifying operations are allowed. Example: Query all users with age greater than 18.
AI agents call query to retrieve information from PostgreSQL MCP Server without modifying anything — typically the context-gathering step in research, monitoring, and reporting workflows, before the agent takes action elsewhere.
The tool is strictly limited to read-only operations (SELECT and equivalent non-modifying SQL). It cannot create, modify, delete, or execute arbitrary code. The explicit restriction to non-modifying operations and the example use case (querying data) confirm this is a pure Read category tool with low severity.
From the tool's definition Tool description explicitly states 'Run a read-only SQL query' and 'retrieve data without modifying the database. Only SELECT statements and other non-modifying operations are allowed.'
Risk signalsBulk/mass operation — affects multiple targets
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 PostgreSQL MCP Server, 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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Run a read-only SQL query against the PostgreSQL database and return the results as JSON. Use this tool to retrieve data without modifying the database. Only SELECT statements and other non-modifying operations are allowed. Example: Query all users with age greater than 18. It is categorised as a Read tool in the PostgreSQL MCP Server MCP Server, which means it retrieves data without modifying state.
Register the PostgreSQL MCP Server 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 MCP Server. 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 MCP server (vignesh-codes/ai-agents-mcp-pg). PolicyLayer sits as a proxy in front of this server to enforce policies before tool calls reach the server.
Start from PostgreSQL MCP Server, add the rest of your stack, and see everything your agents can call. Then put policy on all of it.
Free to start. No card required.
6 PostgreSQL MCP Server tools catalogued and risk-classified — across an index of 43,000+ MCP servers.