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db_query

Run SQL queries with role-based permissions, enforcing read, write, and delete restrictions across PostgreSQL, MySQL, and SQLite databases.

Instructions

Run a SQL query. SELECT/SHOW requires db.read. INSERT/UPDATE requires db.write.. DELETE/DROP requires db.danger.. Supports PostgreSQL, MySQL, SQLite.

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": {
      "query": "<query>"
    },
    "name": "db_query"
  }
}

Input Schema

Name	Required	Description	Default
`query`	Yes	SQL query to execute
`database`	No	Database URL (optional, uses GUARD_DB_URL env var if not provided)

Schema Changelog

Changes observed during successful MCP inspections.

First observedv0.1.1Aug 2, 2026

TDQS

A4.2/5.0

Behavior4/5

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

Since no annotations are provided, the description carries the full burden. It discloses the permission model: SELECT/SHOW requires db.read, INSERT/UPDATE requires db.write.*, DELETE/DROP requires db.danger.*. This is valuable behavioral insight not evident from the schema alone, though it doesn't mention return formats or error handling.

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 concise: four short sentences, each adding value. It leads with the purpose and quickly covers permissions and supported databases, with no redundant phrases or unnecessary details.

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 tool that can execute arbitrary SQL, the description covers essential context: purpose, permission requirements, and supported DBs. It lacks explicit warnings about destructive operations or return behavior, but the permission hints for DELETE/DROP mitigate that. The tool is adequately specified for an agent to select and invoke it correctly.

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 both parameters ('SQL query to execute' and 'Database URL (optional, uses GUARD_DB_URL env var if not provided)'). The description does not add additional parameter-specific detail, so the baseline of 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?

The description opens with 'Run a SQL query', clearly stating the verb and resource. It distinguishes itself from sibling tools by listing supported database types (PostgreSQL, MySQL, SQLite), making it unambiguous versus shell_run or http_request.

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 implies usage context: when you need to execute SQL, this is the tool. It lists supported databases, giving clear context. No explicit when-not or alternatives are named, but none are necessary given the sibling tools are unrelated to direct SQL execution.

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