comfyui-mcp

describe_tool

Retrieves the full description and JSON Schema for a specific ComfyUI MCP tool, so you can inspect required parameters before calling it for the first time.

Instructions

Get the full description and JSON Schema of one tool from the catalog. Always call this before the first call_tool of a tool you haven't used in this session.

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": "describe_tool"
  }
}

Input Schema

Name	Required	Description	Default
`name`	No	Exact tool name from list_tools.
`tool_name`	No	Alias for name.

Schema Changelog

Changes observed during successful MCP inspections.

First observedv1.0.0Sep 30, 2026

TDQS

A4.5/5.0

Behavior4/5

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

With no annotations provided, the description carries a moderate burden. It describes what the tool returns ('full description and JSON Schema') and notes it comes 'from the catalog,' implying a read-only lookup. It does not explicitly state 'no side effects' or discuss error behavior, but for a trivial describe tool, this is acceptable and adds useful context about session-based best practice.

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 sentences, zero filler. The primary purpose is front-loaded in the first sentence, and the second sentence delivers a crucial usage directive. Every word earns its place.

Shorter descriptions cost fewer tokens and are easier for agents to parse. Every sentence should earn its place.

Completeness5/5

Given the tool's complexity, does the description cover enough for an agent to succeed on first attempt?

The tool is simple (no output schema, no annotations, two self-explanatory parameters). The description fully covers its purpose, its role in the workflow, and hints at return content. Given the low complexity, this is complete and well-contextualized.

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?

The input schema already provides 100% parameter coverage: 'name' is described as 'Exact tool name from list_tools' and 'tool_name' as 'Alias for name.' The description adds no additional parameter semantics beyond the schema, so the baseline of 3 is 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 clearly states a specific verb and resource: 'Get the full description and JSON Schema of one tool from the catalog.' This distinguishes it from siblings like list_tools (which lists all tools) and call_tool (which invokes a tool). The purpose is unambiguous and non-tautological.

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

Usage Guidelines5/5

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

The description provides explicit when-to-use guidance: 'Always call this before the first call_tool of a tool you haven't used in this session.' This directly instructs the agent on the proper workflow and implies it should be used as a prerequisite for unfamiliar tools, making the usage context crystal clear.

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