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MCPg - Production-grade PostgreSQL MCP Server

MCPg - Production-grade PostgreSQL MCP Server

by devopam
OverviewSchemaSourceRelated ServersDiscussionsAdmin
Python
Hybrid

List grants

list_grants
Read-only

List table privileges to reveal who can SELECT, INSERT, UPDATE, DELETE, TRUNCATE, REFERENCE, or TRIGGER and whether each grantee can regrant.

Instructions

List the privileges granted on a table — who may do what to it. Returns a list of objects with grantee, privilege (SELECT / INSERT / UPDATE / DELETE / TRUNCATE / REFERENCES / TRIGGER), grantable (bool — may the grantee regrant), and grantor.

Tool call template

Replace each placeholder with a value matching the input schema. Only required parameters are included; add optional parameters as needed.

{
  "id": 1,
  "jsonrpc": "2.0",
  "method": "tools/call",
  "params": {
    "arguments": {
      "schema": "<schema>",
      "table": "<table>"
    },
    "name": "list_grants"
  }
}

Input Schema

NameRequiredDescriptionDefault
tableYes
schemaYes
databaseNoOptional: a database id from list_databases, to target a configured secondary (read-only) database; omit for the primary. Database names that are not configured ids are rejected.

Output Schema

NameRequiredDescriptionDefault
resultYes

Schema Changelog

Changes observed during successful MCP inspections.

  1. Changed1 schema field changedv0.8.4
    • changedInput schema / properties / database / description
      Previous value: -"Optional: target a configured secondary (read-only) database by name; omit for the primary. Call list_databases to see the configured ids."New value: +"Optional: a database id from list_databases, to target a configured secondary (read-only) database; omit for the primary. Database names that are not configured ids are rejected."
  2. First observedv0.6.8

TDQS

A3.5/5.0
Behavior3/5

Does the description disclose side effects, auth requirements, rate limits, or destructive behavior?

Annotations already declare readOnlyHint=true and openWorldHint=false, so the safety profile is covered. The description adds the shape of results (privilege enum, grantable flag, grantor), but that duplicates an output schema that already exists, and it says nothing about behavior on a missing table, column-level grants, or PUBLIC grantees.

Agents need to know what a tool does to the world before calling it. Descriptions should go beyond structured annotations to explain consequences.

Conciseness4/5

Is the description appropriately sized, front-loaded, and free of redundancy?

Two sentences, front-loaded with the core purpose, no filler. The second sentence re-enumerates return fields that the output schema already defines, so it is slightly redundant but still compact.

Shorter descriptions cost fewer tokens and are easier for agents to parse. Every sentence should earn its place.

Completeness3/5

Given the tool's complexity, does the description cover enough for an agent to succeed on first attempt?

For a simple read-only lookup with annotations and an output schema, the essentials are present. However, with two of three parameters undocumented and no guidance on the secondary-database variant or error behavior, an agent could still misinvoke it on non-primary databases.

Complex tools with many parameters or behaviors need more documentation. Simple tools need less. This dimension scales expectations accordingly.

Parameters2/5

Does the description clarify parameter syntax, constraints, interactions, or defaults beyond what the schema provides?

Schema description coverage is only 33% — only `database` is documented. The description never explains `schema` vs `table` addressing or how grants resolve when `database` points at a secondary read-only instance, so it fails to compensate for the coverage gap even though the parameter names are largely self-evident.

Input schemas describe structure but not intent. Descriptions should explain non-obvious parameter relationships and valid value ranges.

Purpose5/5

Does the description clearly state what the tool does and how it differs from similar tools?

States a specific verb and resource ('List the privileges granted on a table') and adds a plain-language gloss ('who may do what to it') that disambiguates it from nearby concepts like roles or RLS policies in the sibling list.

Agents choose between tools based on descriptions. A clear purpose with a specific verb and resource helps agents select the right tool.

Usage Guidelines3/5

Does the description explain when to use this tool, when not to, or what alternatives exist?

Usage is only implied: an agent can infer it should call this when asking who can read or write a given table. There is no explicit when-to-use, no mention of when to prefer list_roles or list_policies instead, and no stated prerequisites such as needing schema/table to exist.

Agents often have multiple tools that could apply. Explicit usage guidance like "use X instead of Y when Z" prevents misuse.

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