create_or_replace_function · Pg MCP: Risk & Policy

WHAT IT DOES

What create_or_replace_function does on Pgmcp

AI agents invoke create_or_replace_function to trigger actions in Pgmcp. 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 create_or_replace_function needs a policy

This tool defines or overwrites executable database functions (stored procedures/functions) in PostgreSQL. It is an Execute-category risk because it installs code that runs inside the database engine. If misused, an agent could create malicious functions with elevated privileges, arbitrary SQL execution, or system-level access (e.g., via PL/pgSQL or PL/Python).

From the tool's definition Create or replace a function in the PostgreSQL database

Attacks that exploit this kind of access

Recommended rule Ready

Verdict

create_or_replace_function Rate-limited

create_or_replace_function 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": {
    "create_or_replace_function": {
      "limits": [
        {
          "counter": "create_or_replace_function_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 Pgmcp, so you can run agents against it safely.

FAQ

Questions about create_or_replace_function

What does the create_or_replace_function tool do? +

Create or replace a function in the PostgreSQL database. It is categorised as a Execute tool in the Pgmcp MCP Server, which means it can trigger actions or run processes. Use rate limits and argument validation.

How do I enforce a policy on create_or_replace_function? +

Register the Pg MCP server in PolicyLayer and add a rule for create_or_replace_function: 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 Pgmcp. Nothing to install.

What risk level is create_or_replace_function? +

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

Can I rate-limit create_or_replace_function? +

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

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

create_or_replace_function is provided by the Pg MCP server (veloper/pgmcp). PolicyLayer sits as a proxy in front of this server to enforce policies before tool calls reach the server.