# 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…

- **Type:** Skill
- **Install:** `agentstack add skill-agent-skills-hub-agent-skills-hub-agent-tool-builder`
- **Verified:** Yes — security-reviewed for prompt injection and unsafe behavior
- **Seller:** [agent-skills-hub](https://agentstack.voostack.com/s/agent-skills-hub)
- **Installs:** 0
- **Category:** [AI & ML](https://agentstack.voostack.com/c/ai-and-ml)
- **Latest version:** 0.1.0
- **License:** MIT
- **Upstream author:** [agent-skills-hub](https://github.com/agent-skills-hub)
- **Source:** https://github.com/agent-skills-hub/agent-skills-hub/tree/main/skills/agent-tool-builder
- **Website:** https://agent-skills-hub.github.io/

## Install

```sh
agentstack add skill-agent-skills-hub-agent-skills-hub-agent-tool-builder
```

Requires the [AgentStack CLI](https://agentstack.voostack.com/docs/cli). Works with Claude Code, Cursor, and any MCP-compatible agent.

## About

# Agent Tool Builder

You are an expert in the interface between LLMs and the outside world.
You've seen tools that work beautifully and tools that cause agents to
hallucinate, loop, or fail silently. The difference is almost always
in the design, not the implementation.

Your core insight: The LLM never sees your code. It only sees the schema
and description. A perfectly implemented tool with a vague description
will fail. A simple tool with crystal-clear documentation will succeed.

You push for explicit error hand

## Capabilities

- agent-tools
- function-calling
- tool-schema-design
- mcp-tools
- tool-validation
- tool-error-handling

## Patterns

### Tool Schema Design

Creating clear, unambiguous JSON Schema for tools

### Tool with Input Examples

Using examples to guide LLM tool usage

### Tool Error Handling

Returning errors that help the LLM recover

## Anti-Patterns

### ❌ Vague Descriptions

### ❌ Silent Failures

### ❌ Too Many Tools

## Related Skills

Works well with: `multi-agent-orchestration`, `api-designer`, `llm-architect`, `backend`

## Source & license

This open-source skill is cataloged on AgentStack and links to its original source — we do not rehost the code.

- **Author:** [agent-skills-hub](https://github.com/agent-skills-hub)
- **Source:** [agent-skills-hub/agent-skills-hub](https://github.com/agent-skills-hub/agent-skills-hub)
- **License:** MIT
- **Homepage:** https://agent-skills-hub.github.io/

Install and usage instructions live in the source repository linked above.

## Pricing

- **Free** — Free

## Security capabilities

Automated source analysis of v0.1.0 — what this tool can access:

- **Network access:** no
- **Filesystem access:** no
- **Shell / process execution:** no
- **Environment & secrets:** no
- **Dynamic code execution:** no

*"Yes" means the capability is present in the source — more access means more to trust, not that it is unsafe.*


## Versions

- **0.1.0** — security scan: passed — Imported from the upstream source.

## Links

- Listing page: https://agentstack.voostack.com/l/skill-agent-skills-hub-agent-skills-hub-agent-tool-builder
- Seller: https://agentstack.voostack.com/s/agent-skills-hub
- Browse the marketplace: https://agentstack.voostack.com/browse

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Listed on AgentStack — the marketplace for AI agent skills and MCP servers. Every listing is security-reviewed. Creators keep 70%.