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MCPg - Production-grade PostgreSQL MCP Server

MCPg - Production-grade PostgreSQL MCP Server

by devopam
OverviewSchemaSourceRelated ServersDiscussionsAdmin
Python
Hybrid

Get prewarm extension status

get_prewarm_extension_status
Read-only

Report whether pg_prewarm and pg_buffercache are installed and if autoprewarm is enabled in shared_preload_libraries, so you can verify prerequisites before warming the buffer cache.

Instructions

Report whether pg_prewarm (and the supporting pg_buffercache) are installed, and whether pg_prewarm is listed in shared_preload_libraries (the autoprewarm worker requires it). Returns an object with pg_prewarm_installed (bool), pg_buffercache_installed (bool), autoprewarm_libraries_present (bool), and shared_preload_libraries (the raw setting).

Example: get_prewarm_extension_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_prewarm_extension_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
pg_prewarm_installedYes
pg_buffercache_installedYes
shared_preload_librariesYes
autoprewarm_libraries_presentYes

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

A4/5.0
Behavior4/5

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

Annotations already declare readOnlyHint=true and openWorldHint=false, so the safety profile is covered. The description still adds real context beyond the annotations by explaining why shared_preload_libraries matters (the autoprewarm worker requires it) and enumerating the four boolean/raw fields returned.

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?

The definition is front-loaded with the core check, then the return shape, then an example. The trailing no-argument example is nearly redundant but short and harmless; nothing else is wasted.

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

Completeness5/5

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

With an output schema, one optional fully-documented parameter, and annotations covering safety, the description fills the remaining gaps: the semantic meaning of each field and the operational prerequisite it detects. An agent can call it correctly with no further information.

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?

Schema coverage is 100%; the single optional `database` parameter is fully documented in the schema as a configured secondary database id from list_databases. The description adds nothing about that parameter, which is acceptable given the schema baseline but earns no extra credit.

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?

The description states a specific verb (report), resource (pg_prewarm/pg_buffercache installation state and shared_preload_libraries membership), and explains the reason (the autoprewarm worker requires the entry). This lets an agent distinguish it from generic siblings such as list_extensions or list_prewarmed_relations.

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?

The description implies the use case — verifying prerequisites before autoprewarm-related work — but never explicitly says when to call this instead of list_extensions, list_prewarmed_relations, or recommend_prewarm_targets, and gives no exclusions. The usage context is inferable but not spelled out.

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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