alter_table · MCP PostgreSQL Server MCP: Risk & Policy

WHAT IT DOES

What alter_table does on MCP PostgreSQL Server

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

WHY IT NEEDS A POLICY

Why alter_table needs a policy

ALTER TABLE commands modify table schemas (add/drop columns, change constraints, rename objects, etc.) in a reversible manner. This is a Write operation as modifications can theoretically be undone with subsequent ALTER commands. Severity is high because schema modifications can break application logic, cause downtime, or corrupt data dependencies.

From the tool's definition Tool name 'alter_table' and description 'Modify an existing table structure' indicate structural modifications to database tables.

Attacks that exploit this kind of access

Recommended rule Ready

Verdict

alter_table Rate-limited

alter_table 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": {
    "alter_table": {
      "limits": [
        {
          "counter": "alter_table_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 MCP PostgreSQL Server, so you can run agents against it safely.

FAQ

Questions about alter_table

What does the alter_table tool do? +

Modify an existing table structure. It is categorised as a Write tool in the MCP PostgreSQL Server MCP Server, which means it can create or modify data. Consider rate limits to prevent runaway writes.

How do I enforce a policy on alter_table? +

Register the MCP PostgreSQL Server MCP server in PolicyLayer and add a rule for alter_table: 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 MCP PostgreSQL Server. Nothing to install.

What risk level is alter_table? +

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

Can I rate-limit alter_table? +

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

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

alter_table is provided by the MCP PostgreSQL Server MCP server (kristofer84/mcp-postgres). PolicyLayer sits as a proxy in front of this server to enforce policies before tool calls reach the server.