Custom Tool Builder
$2.99OfficialCreate production-grade tools/functions that AI agents can call: define schemas, implement handlers, add validation and error handling.
What you get
- ✓10-step procedure
- ✓6 pitfalls to avoid
- ✓Installs into 6 tools
- Version
- v1 →
- Last updated
- today
- Length
- 5 min read
- Requires
- Best with a strong model (Claude Sonnet 4)
Works in: Claude Code, Codex, Cline, opencode, OpenClaw, Hermes · Handles multi-file projects
Preview
When to use
Use this skill when the user needs to build a tool, function, or capability that an AI agent can invoke: "add a tool that queries our database," "let the agent send Slack messages," "create a function the model can call." Trigger phrases: tool, function calling, tool use, MCP tool, agent capability, function schema. Also use it when reviewing an existing tool that agents misuse — the schema or description is almost always the culprit.
Do NOT use it for building entire MCP servers (use an MCP scaffolder skill), or for prompts/instructions. This is about the atomic unit: one tool, its schema, its handler, and its error contract.
Inputs to gather
- **The agent's actual ta
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