switch_server_db · Postgres MCP: Risk & Policy

WHAT IT DOES

What switch_server_db does on Postgres

AI agents use switch_server_db to create or update resources in Postgres — usually the action step of a workflow, after the agent has gathered context. Every call changes real data in your Postgres environment.

WHY IT NEEDS A POLICY

Why switch_server_db needs a policy

This tool changes the connection context/state of the MCP session, which is a reversible modification to session state rather than read-only retrieval. While not permanently destructive, connecting to an arbitrary database could enable downstream malicious queries if an AI agent is manipulated to switch to unintended databases.

From the tool's definition Tool description states 'Connect to a PostgreSQL server and database' which modifies the active connection state. The tool name 'switch_server_db' indicates it changes the server/database context, which is a state-modifying operation.

Attacks that exploit this kind of access

Recommended rule Ready

Verdict

switch_server_db Rate-limited

switch_server_db stays usable, but capped — an agent stuck in a loop can't make hundreds of changes a minute. Everything else on the server is denied unless you say otherwise.

View as policy code

policy.json

{
  "version": "1",
  "default": "deny",
  "tools": {
    "switch_server_db": {
      "limits": [
        {
          "counter": "switch_server_db_rate",
          "window": "minute",
          "max": 30,
          "scope": "grant"
        }
      ]
    }
  }
}

LIMIT THIS TOOL →

Instant setup, no code required.

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

FAQ

Questions about switch_server_db

What does the switch_server_db tool do? +

Connect to a PostgreSQL server and database. MUST be called before executing queries. Use list_servers to find server names, list_databases to find database names. It is categorised as a Write tool in the Postgres MCP Server, which means it can create or modify data. Consider rate limits to prevent runaway writes.

How do I enforce a policy on switch_server_db? +

Register the Postgres MCP server in PolicyLayer and add a rule for switch_server_db: 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.

What risk level is switch_server_db? +

switch_server_db is a Write tool with medium risk. Write tools should be rate-limited to prevent accidental bulk modifications.

Can I rate-limit switch_server_db? +

Yes. Add a rate_limit block to the switch_server_db 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 switch_server_db completely? +

Set action: deny in the PolicyLayer policy for switch_server_db. 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 switch_server_db? +

switch_server_db is provided by the Postgres MCP server (teja-sudo/postgres-mcp-server). PolicyLayer sits as a proxy in front of this server to enforce policies before tool calls reach the server.