pg-insight-mcp

Run query

run_query

Read-onlyIdempotent

Execute a single read-only SQL statement in a guarded transaction, with capped results marked truncated when additional rows exist. Use it to safely inspect PostgreSQL data without writes or DDL.

Instructions

Run a single read-only SQL statement inside a read-only transaction. Results are capped and marked as truncated when more rows exist.

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": {
      "sql": "<sql>"
    },
    "name": "run_query"
  }
}

Input Schema

Name	Required	Description	Default
`sql`	Yes
`max_rows`	No

Output Schema

Name	Required	Description	Default
No arguments

Schema Changelog

Changes observed during successful MCP inspections.

First observedv0.1.0Nov 5, 2026

TDQS

A3.5/5.0

Behavior4/5

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

Annotations already establish read-only, idempotent, non-destructive behavior. The description adds meaningful context beyond that: statements execute inside a read-only transaction, only one statement is allowed, and result sets are capped and marked as truncated when more rows exist. It could still say more about the cap behavior and max_rows interaction.

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?

Two compact sentences with no wasted wording. The most important constraint, read-only single-statement execution, is front-loaded.

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 output schema exists, so return values need not be described in detail. The description covers transaction safety and truncation, but with 0% schema coverage it omits critical parameter meaning, especially what max_rows does and what the default cap is, which matters for correct invocation.

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

Parameters2/5

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

Schema description coverage is 0%, so the description must compensate for both parameters. It hints at a row cap but does not explain the sql parameter's constraints or how max_rows overrides or interacts with the default cap, leaving parameter semantics largely undocumented.

Input schemas describe structure but not intent. Descriptions should explain non-obvious parameter relationships and valid value ranges.

Purpose4/5

Does the description clearly state what the tool does and how it differs from similar tools?

The description states a specific verb and resource: running a single read-only SQL statement in a read-only transaction. It is clearly a query-execution tool, though it does not explicitly differentiate itself from siblings such as explain_query or sample_rows.

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?

Usage is implied: it is for executing read-only SQL, and the 'single statement' constraint helps frame when it applies. However, the description does not explicitly say when to prefer it over explain_query or sample_rows, nor does it state when not to use it.

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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