Tool Design
API & Tools$99
A tool definition design skill built on the #1 principle: THE DESCRIPTION IS KING. Claude decides which tool to use based on the description, not the name. This skill walks through the complete tool definition checklist — name, description (with trigger conditions, output format, and disambiguation), input schema with constraints, error response patterns, and tool_choice strategies. Includes MCP server considerations. Built from analysis of thousands of expert practitioners on Claude API tool design.
What's Inside
Tool description writing (trigger, output, disambiguation)
Input schema design with types & constraints
Error response patterns for tool failures
tool_choice strategy (auto, any, specific tool)
MCP server design considerations
Real-world examples from production systems
Skill Preview
tool-design.md
---
name: tool-design
description: Design Claude API tool definitions with proper descriptions.
---
# Tool Design for Claude API
Design tool definitions that Claude will use effectively.
The #1 principle: THE DESCRIPTION IS KING.
## Tool Definition Checklist
For each tool, define:
### 1. Name
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Works with Claude Code, Cursor & Codex CLI
Claude CodeCursorCodex CLI