mcp-postgres

pg_constraint_list

List primary key, foreign key, unique, and check constraints for a specified PostgreSQL table to inspect its schema and integrity rules.

Instructions

List constraints (primary key, foreign key, unique, check) for a table.

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>",
      "table": "<table>"
    },
    "name": "pg_constraint_list"
  }
}

Input Schema

Name	Required	Description
`table`	Yes	Table name
`schema`	No	Schema name (default: 'public')
`target`	Yes	Target name from ~/.dbx/targets/

Schema Changelog

Changes observed during successful MCP inspections.

First observedv2026.4.10-3Jul 25, 2026

TDQS

B3.3/5.0

Behavior2/5

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

No annotations are provided, so the description must fully convey behavior. It states 'List constraints' which implies a read-only operation, but lacks details on required permissions, error scenarios (e.g., table not found), or output structure. For a simple list tool, minimal behavioral disclosure is acceptable but insufficient given no annotations.

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 a single, well-structured sentence of 10 words. It front-loads the action and resource without any filler, making it highly efficient and easy to parse.

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?

The tool is simple with no output schema, so the description provides basic input context. However, it omits information about the return format (e.g., constraint names, types, columns). For a listing tool, users would benefit from knowing what data is returned. Overall, adequate but not thorough.

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% with descriptions for all three parameters. The description reiterates the context ('for a table') but adds no extra meaning beyond the schema for individual parameters. Baseline 3 is appropriate as the schema already documents parameters adequately.

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 verb ('List'), the resource ('constraints'), and specifies the context ('for a table') with explicit constraint types (primary key, foreign key, unique, check). It effectively distinguishes this tool from siblings like pg_table_list or pg_index_list by naming the exact object being listed.

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

Usage Guidelines2/5

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

No explicit guidance on when to use this tool vs alternatives. While the purpose is clear, the description does not advise on appropriate contexts, prerequisites (e.g., connection needed), or situations where this tool should not be used. Users must infer applicability from the tool name.

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