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MCPg - Production-grade PostgreSQL MCP Server

MCPg - Production-grade PostgreSQL MCP Server

by devopam
OverviewSchemaSourceRelated ServersDiscussionsAdmin
Python
Hybrid

Get PGQ status

get_pgq_status
Read-only

Reports whether SQL/PGQ property graph queries are usable on this PostgreSQL server, returning availability, version, and guidance so agents can choose SQL/PGQ or fall back to Cypher.

Instructions

Report whether SQL/PGQ (the SQL standard for property graph queries, new in PG 19) is usable on this server. SQL/PGQ coexists with the AGE-style graph_operations bucket — get_pgq_status is the agent's hint about which surface to reach for. Never raises; on PG < 19 reports available=false with a diagnostic pointing at run_cypher. Returns an object with available (bool), server_version_num (int), server_version (the human-readable string), and detail (a guidance string the agent can surface to the user).

Example: get_pgq_status()

Tool call template

This tool declares no required parameters. Add optional parameters from the input schema as needed.

{
  "id": 1,
  "jsonrpc": "2.0",
  "method": "tools/call",
  "params": {
    "arguments": {},
    "name": "get_pgq_status"
  }
}

Input Schema

NameRequiredDescriptionDefault
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
detailYes
availableYes
server_versionYes
server_version_numYes

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

A4.3/5.0
Behavior4/5

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

Annotations already declare readOnlyHint=true and openWorldHint=false, so safety is covered; the description adds genuinely new behavior beyond them — 'Never raises' and the PG < 19 degradation path with an embedded diagnostic. It stops short of saying how version detection is performed or whether anything is required of the caller, so it is strong but not exhaustive.

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?

Front-loaded with the core question, then the routing role, then failure behavior. The enumerated return fields (`available`, `server_version_num`, `server_version`, `detail`) partially duplicate the output schema, which is the only wasted material; otherwise tight.

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

Completeness4/5

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

An output schema exists and annotations cover read-only safety, so the description need only carry the version gate and routing logic — both are present. The one omission is that it never connects the `database` parameter to the version check (a configured secondary may be a different major version), which mildly matters for interpreting `available` on non-primary targets.

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

Parameters3/5

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

The single `database` parameter is fully documented in the schema (100% coverage, including the secondary read-only targeting and rejection of unconfigured names), and the description says nothing about it. Baseline 3 applies since the schema carries the full parameter burden; the description does not compensate for or extend it.

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+resource ('Report whether SQL/PGQ ... is usable on this server') and immediately differentiates the two graph surfaces, naming the AGE-style `graph_operations` bucket and `run_cypher` as the alternatives. An agent can tell this apart from the other graph tools without opening any schema.

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

Usage Guidelines5/5

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

Explicitly frames the tool as the routing probe ('the agent's hint about which surface to reach for') and gives the fallback path: on PG < 19 it reports available=false with a diagnostic pointing at `run_cypher`. That is both a when-to-use rule and a named alternative with the condition that selects it.

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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