createIndex · Postgresql MCP: Risk & Policy

WHAT IT DOES

What createIndex does on Postgresql

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

WHY IT NEEDS A POLICY

Why createIndex needs a policy

Creating an index is a reversible schema modification (indexes can be dropped). It does not delete data and is not destructive. While it can affect performance if poorly chosen, the operation itself is Write-category—it creates new database structures. It is less severe than Destructive (which cannot be undone) but more severe than Read.

From the tool's definition Tool description states 'Create a new index on a table' and 'creates it CONCURRENTLY'. Index creation modifies database schema structures and is a Write operation that creates new metadata objects.

Attacks that exploit this kind of access

Recommended rule Ready

Verdict

createIndex Rate-limited

createIndex 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": {
    "createIndex": {
      "limits": [
        {
          "counter": "createindex_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 Postgresql, so you can run agents against it safely.

FAQ

Questions about createIndex

What does the createIndex tool do? +

Create a new index on a table. By default creates it CONCURRENTLY (non-blocking for reads/writes). Specify columns to index, whether it. It is categorised as a Write tool in the Postgresql MCP Server, which means it can create or modify data. Consider rate limits to prevent runaway writes.

How do I enforce a policy on createIndex? +

Register the Postgresql MCP server in PolicyLayer and add a rule for createIndex: 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. Nothing to install.

What risk level is createIndex? +

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

Can I rate-limit createIndex? +

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

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

createIndex is provided by the Postgresql MCP server (vnikhilbuddhavarapu/postgresql-mcp). PolicyLayer sits as a proxy in front of this server to enforce policies before tool calls reach the server.