Agent skill · software engineering · aiskillstore
agent-tool-builder
Tools are how AI agents interact with the world. A well-designed
Why this skill is useful
Provides detailed guidance on JSON Schema and MCP standards for tool design that the AI wouldn't reliably generate on its own.
What it needs
About 9k tokens when loaded. Last updated 2026-08-07. 405 stars on the source repository.
What this skill does
Agent Tool Builder Tools are how AI agents interact with the world. A well-designed tool is the difference between an agent that works and one that hallucinates, fails silently, or costs 10x more tokens than necessary. This skill covers tool design from schema to error handling. JSON Schema best practices, description writing that actually helps the LLM, validation, and the emerging MCP standard that's becoming the lingua franca for AI tools. Key insight: Tool descriptions are more important than tool implementations. The LLM never sees your code - it only sees the schema and description. Principles Description quality > implementation quality for LLM accuracy Aim for fewer than 20 tools - more causes confusion Every tool needs explicit error handling - silent failures poison agents Return strings, not objects - LLMs process text Validation gates before execution - reject, fix, or escalate, never silent fail Test tools with the LLM, not just unit tests Capabilities agent-tools function-calling tool-schema-design mcp-tools tool-validation tool-error-handling Scope multi-agent-coordination → multi-agent-orchestration agent-memory → agent-memory-systems api-design → api-designer llm-prompting → prompt-engineering Tooling Standards JSON Schema - When: All tool definitions Note: The universal format for tool schemas MCP (Model Context Protocol) - When: Building reusable, cross-platform tools Note: Anthropic's open standard, widely adopted Frameworks Anthropic SDK - When: Claude-based agents Note: Beta tool runner handles most complexity OpenAI Functions - When: OpenAI-based agents Note: Use strict mode for guaranteed schema compliance Vercel AI SDK - When: Multi-provider tool handling Note: Abstracts differences between providers LangChain Tools - When: LangChain-based agents Note: Converts MCP tools to LangChain format Patterns Tool Schema Design Creating clear, unambiguous JSON Schema for tools When to use: Defining any new tool for an agent TOOL SCHEMA BEST PRACTICES: …
How to use it
Reference it in AdaL, Claude Code, Cursor or any coding agent — nothing to install:
@skills aiskillstore/agent-tool-builder