pg_exists

Check if rows exist in a table. WHERE clause is optional: with WHERE = checks matching rows; without WHERE = checks if table has any rows at all. For table *schema* existence, use pg_list_tables.

SERVERPostgreSQL MCP Server SOURCE@neverinfamous/postgres-mcp

Low RISK CLASS

Category Read

Parameters 00 required

Recommended Allowedsee the rule below

Registry record Grade F, identity unverified Pull the record →

This record as markdown: /tools/io-github-neverinfamous-postgres-mcp/pg-exists.md

WHAT IT DOES

What pg_exists does on PostgreSQL MCP Server

AI agents call pg_exists to retrieve information from PostgreSQL MCP Server without modifying anything. It is typically the context-gathering step in research, monitoring, and reporting workflows, before the agent takes action elsewhere.

RISK

Why pg_exists is rated Low

This is a query operation that retrieves information about data existence without creating, modifying, deleting, or executing side effects. The tool is defensive (recommends pg_list_tables for schema checks) and operates read-only. Low severity because misuse (checking for non-existent rows) has minimal blast radius.

From the tool's definition Tool description explicitly states "Check if rows exist in a table" with optional WHERE clause. No modification, deletion, or execution of arbitrary code—purely a presence check returning a boolean result.

Attacks that exploit this kind of access

RECOMMENDED RULE

The rule that runs pg_exists safely

PolicyLayer is an MCP gateway: it sits between your AI agents and PostgreSQL MCP Server, and checks every tool call against a rule you set before the call runs. Nothing changes on the server itself. For pg_exists, this is the rule to start with:

pg_exists Allowed

pg_exists is read-only, so it stays allowed. Everything else on the server is denied unless you say otherwise.

View as policy code

policy.json

{
  "version": "1",
  "default": "deny",
  "tools": {
    "pg_exists": {}
  }
}

ALLOW ONLY THIS TOOL → Instant setup, no code required.

The button opens the PolicyLayer dashboard: create your workspace, connect PostgreSQL MCP Server, apply this rule, and every pg_exists call is checked against it from then on.

FAQ

Questions about pg_exists

What does the pg_exists tool do? +

Check if rows exist in a table. WHERE clause is optional: with WHERE = checks matching rows; without WHERE = checks if table has any rows at all. For table *schema* existence, use pg_list_tables. It is categorised as a Read tool in the PostgreSQL MCP Server MCP Server, which means it retrieves data without modifying state.

How do I enforce a policy on pg_exists? +

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

What risk level is pg_exists? +

pg_exists is a Read tool with low risk. Read-only tools are generally safe to allow by default.

Can I rate-limit pg_exists? +

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

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

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

KEEP EXPLORING

What pg_exists does on PostgreSQL MCP Server

Why pg_exists is rated Low

The rule that runs pg_exists safely

Questions about pg_exists

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