# Hello Tool

> Demonstrates `skill_mode=tool` by composing two host-supplied callbacks (`echo` + `uppercase`) into one MCP tool. The codegen compiler turns this `tool_schema.steps[]` into a ComposedToolDef; the executor walks the steps at MCP-tool invocation time.

- Skill: `acosmi/hello-tool` (Agent Skill)
- Install (CLI): `npx skillmds@latest add acosmi/hello-tool`
- Raw SKILL.md: https://api.skillmd.com/api/skills/acosmi/hello-tool/raw
- Safety review: pending (external: skill-scanner PASS, skillspector PASS)
- Works with: Claude Code, Claude.ai, OpenAI Codex
- Category: AI & ML
- Author: acosmi (https://skillmd.com/u/acosmi)
- Updated: 2026-09-22
- Page: https://skillmd.com/skills/acosmi/hello-tool

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# Hello, tool!

This SKILL composes two host-registered callbacks (`echo` and
`uppercase`) via the `tool_schema.steps[]` block above. See
`examples/tool-callback-registry.ts` for a reference implementation
of those callbacks.