mcp-postgres

pg_connect

Connect to a configured PostgreSQL server target. Specify a target name if multiple are available, otherwise uses the default target.

Instructions

Connect to a PostgreSQL server target. If multiple targets are configured, specify which one. Otherwise connects to the default target.

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": {
      "target": "<target>"
    },
    "name": "pg_connect"
  }
}

Input Schema

Name	Required	Description	Default
`target`	Yes	Target name from ~/.dbx/targets/
`profile`	No	Named connection profile (optional, uses default if omitted)

Schema Changelog

Changes observed during successful MCP inspections.

First observedv2026.4.10-3Jul 25, 2026

TDQS

A3.9/5.0

Behavior2/5

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

No annotations are provided, placing full burden on the description. The description only mentions connecting but does not disclose side effects (e.g., state changes, error conditions, or whether existing connections are affected). For a tool that establishes a session, this is insufficient.

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

Conciseness5/5

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

The description is two short sentences with no redundant information. It front-loads the core purpose and provides necessary guidance concisely.

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 connection tool with 2 parameters and no output schema, the description covers the basic function but lacks details about the return value (e.g., connection ID or status). The sibling tools suggest connections are managed, so return value context would be helpful.

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

Parameters4/5

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

Schema description coverage is 100% (both parameters described). The description adds value by explaining the target selection logic (multiple vs default), which goes beyond the schema field descriptions. This provides meaningful usage context.

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 clearly states the tool connects to a PostgreSQL server target and explains the default behavior when multiple targets exist. It uses specific verb 'connect' and resource 'PostgreSQL server target', distinguishing it from siblings that perform queries or other operations.

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?

The description advises when to specify a target (if multiple configured) and when the default is used. It does not explicitly state when not to use or provide alternatives, but the context of sibling tools like pg_disconnect implies usage. Some implicit guidance on prerequisites (target configuration) is present.

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