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MCP PostgreSQL Operations

MCP PostgreSQL Operations

by call518
OverviewSchemaSourceRelated ServersDiscussionsAdmin
Python
Hybrid

get_table_size_info

Analyze table sizes and index usage across a PostgreSQL schema to identify storage consumption and resource usage per table.

Instructions

[Tool Purpose]: Analyze size information and index usage of all tables in specified schema

[Exact Functionality]:

  • Retrieve size information of all tables within schema

  • Analyze index size and total size per table

  • Provide table list sorted by size

[Required Use Cases]:

  • When user requests "table size", "schema capacity", "index usage", etc.

  • When storage analysis of specific schema is needed

  • When resource usage status per table needs to be identified

[Strictly Prohibited Use Cases]:

  • Requests for table data deletion or cleanup operations

  • Requests for index creation or deletion

  • Requests for table structure changes

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_table_size_info"
  }
}

Input Schema

NameRequiredDescriptionDefault
schema_nameNoSchema name to analyze (default: "public")public
database_nameNoDatabase name to analyze (uses default database if omitted)

Output Schema

NameRequiredDescriptionDefault
resultYes

Schema Changelog

Changes observed during successful MCP inspections.

  1. Changed2 schema fields changedv3.4.3
    • addedInput schema / properties / database_name / description
      Added value: +"Database name to analyze (uses default database if omitted)"
    • addedInput schema / properties / schema_name / description
      Added value: +"Schema name to analyze (default: \"public\")"
  2. Changed7 schema fields changedv3.4.2
    • addedInput schema / additionalProperties
      Added value: +false
    • addedInput schema / properties / database_name / anyOf
      Added value: +[
+  {
+    "type": "string"
+  },
+  {
+    "type": "null"
+  }
+]
    • removedInput schema / properties / database_name / title
      Removed value: -"Database Name"
    • removedInput schema / properties / database_name / type
      Removed value: -"string"
    • removedInput schema / properties / schema_name / title
      Removed value: -"Schema Name"
    • removedOutput schema / properties / result / title
      Removed value: -"Result"
    • removedOutput schema / title
      Removed value: -"_WrappedResult"
  3. Addedv1.0.0

TDQS

A3.8/5.0
Behavior3/5

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

No annotations are provided, so the description carries the full behavioral burden. It implies a read-only analysis tool through prohibited use cases and describes sorted output, but it does not explicitly state side-effect safety, required permissions, or performance/rate-limit characteristics.

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

Conciseness3/5

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

The purpose is front-loaded and the sectioned structure is clear, but it is more verbose than needed for a two-parameter read-only tool. The purpose statement and functionality bullets overlap, and the prohibited-use section is somewhat repetitive for the task.

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?

For a read-only analysis tool with high schema coverage and an output schema, the description is largely complete: it defines scope, functionality, and exclusions. The main missing context is explicit confirmation that the operation is safe/read-only and any privilege requirements.

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 description coverage is 100%, so both parameters are already documented with defaults and meanings in the schema. The description adds schema-level scope but does not add syntax or format details beyond what the schema provides, making the baseline 3 appropriate.

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 and resource: analyze size information and index usage for all tables in a specified schema. It also specifies sorted-by-size output and scope, which makes it distinguishable from siblings such as get_table_list or get_index_usage_stats.

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 explicit required use cases, including 'table size', 'schema capacity', and 'index usage', plus strictly prohibited cases such as deletion, index changes, and table structure changes. It does not name alternative sibling tools, so it falls short of full when-to-use-vs-alternatives guidance.

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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