postgres_query · Gmail & PostgreSQL MCP Server MCP

WHAT IT DOES

What postgres_query does on Gmail & PostgreSQL MCP Server

AI agents invoke postgres_query to trigger actions in Gmail & PostgreSQL MCP Server. What it does depends on the arguments the agent supplies, and its effects often reach beyond the immediate call — builds kicked off, notifications sent, workflows started.

WHY IT NEEDS A POLICY

Why postgres_query needs a policy

Although described as read-only SELECT queries, the tool executes arbitrary SQL against a PostgreSQL database. There is no guarantee that the server enforces read-only semantics at the database level, and a misconfigured or manipulated query could expose sensitive data at scale. It falls under Execute because it actively runs code/queries on an external system.

From the tool's definition 'Execute a SELECT query on PostgreSQL database' — the tool runs arbitrary SQL queries against a database.

Attacks that exploit this kind of access

Recommended rule Ready

Verdict

postgres_query Rate-limited

postgres_query stays usable, but rate-capped — a runaway agent can't fire it dozens of times a minute. Everything else on the server is denied unless you say otherwise.

View as policy code

policy.json

{
  "version": "1",
  "default": "deny",
  "tools": {
    "postgres_query": {
      "limits": [
        {
          "counter": "postgres_query_rate",
          "window": "minute",
          "max": 10,
          "scope": "grant"
        }
      ]
    }
  }
}

RATE-LIMIT THIS TOOL →

Instant setup, no code required.

PolicyLayer is an MCP gateway: every tool call is checked against your rule before it reaches Gmail & PostgreSQL MCP Server, so you can run agents against it safely.

FAQ

Questions about postgres_query

What does the postgres_query tool do? +

Execute a SELECT query on PostgreSQL database. Returns read-only results. It is categorised as a Execute tool in the Gmail & PostgreSQL MCP Server MCP Server, which means it can trigger actions or run processes. Use rate limits and argument validation.

How do I enforce a policy on postgres_query? +

Register the Gmail & PostgreSQL MCP Server MCP server in PolicyLayer and add a rule for postgres_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 Gmail & PostgreSQL MCP Server. Nothing to install.

What risk level is postgres_query? +

postgres_query is a Execute tool with high risk. Execute tools should be rate-limited and have argument validation enabled.

Can I rate-limit postgres_query? +

Yes. Add a rate_limit block to the postgres_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.

How do I block postgres_query completely? +

Set action: deny in the PolicyLayer policy for postgres_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.

What MCP server provides postgres_query? +

postgres_query is provided by the Gmail & PostgreSQL MCP Server MCP server (marouanemkm/gmail-mcp-server). PolicyLayer sits as a proxy in front of this server to enforce policies before tool calls reach the server.