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MCPg - Production-grade PostgreSQL MCP Server

MCPg - Production-grade PostgreSQL MCP Server

by devopam
OverviewSchemaSourceRelated ServersDiscussionsAdmin
Python
Hybrid

Get AIO status

get_aio_status
Read-only

Report whether PostgreSQL 19's async-I/O subsystem is usable, returning availability, I/O method and worker settings; on older versions, returns diagnostic guidance to existing I/O tools.

Instructions

Report whether PG 19's async-I/O subsystem is usable. On PG < 19 returns available=false with a diagnostic pointing the agent at the existing read_pg_stat_io / run_maintenance tools. Never raises — driver-level errors during the version or settings probe also surface as available=false. Returns an object with available (bool), server_version_num (int), server_version, io_method ('sync' / 'worker' / 'io_uring' / null), io_min_workers, io_max_workers, and detail (a guidance string).

Example: get_aio_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_aio_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
io_methodYes
io_max_workersYes
io_min_workersYes
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

A4.2/5.0
Behavior4/5

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

Annotations already cover read-only safety, but the description adds genuinely new behavioral facts: the tool never raises and driver-level probe errors degrade to available=false. That error-contract detail is exactly what an agent needs to branch on. The enumerated return fields are useful but partly duplicate the existing output schema.

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 purpose, then the degradation behavior, then the return shape, with a call example at the end. The long field enumeration is slightly wasteful since an output schema exists, but nothing is confusing or padded.

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?

For a zero-required-parameter status probe with annotations and an output schema, everything an agent needs to decide and call is present: version gating, failure semantics, and fallback tooling.

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?

There is one optional parameter with 100% schema description coverage, and the schema already explains the database id targeting and rejection of unconfigured names. The description adds nothing about the parameter, so baseline 3 applies.

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?

Names a specific resource and scope: 'whether PG 19's async-I/O subsystem is usable', with the version boundary stated explicitly. It is clearly distinct from the sibling I/O tools (read_pg_stat_io, run_maintenance) which it routes to rather than duplicates.

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

Usage Guidelines4/5

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

It gives a clear usage condition (checking PG 19 async-I/O availability) and explicitly names the fallback path for PG < 19 via the diagnostic pointing at read_pg_stat_io / run_maintenance. It does not, however, position itself relative to recommend_io_method, which is the closest sibling for I/O method advice.

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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