Use tool-use-schema-writer

Takes a function description (name, purpose, parameters) and writes a valid Anthropic tool_use JSON schema, with type annotations, required fields, and a description for…

Takes a function description (name, purpose, parameters) and writes a valid Anthropic tool_use JSON schema, with type annotations, required fields, and a description for each parameter. Adds a Python client.messages.create(tools=[...]) snippet only when asked.

Reach for it when wiring a Claude agent to a function or API, designing tools for a multi-agent system, or documenting an existing tool for agent consumption.

Install it

npx skilldrop-cli install tool-use-schema-writer                 # Claude Code, your user folder
npx skilldrop-cli install tool-use-schema-writer --project       # Claude Code, this repo
npx skilldrop-cli install tool-use-schema-writer --ide cursor    # or kiro, codex, antigravity, copilot

It is part of the API builder pack: --pack api-builder installs it with its neighbours.

Ask for it

Say it the way you would to a colleague. Requests like these route to it:

• "Write the tool_use JSON schema for this function so Claude can call it"
• "Turn this TypeScript API client method into an Anthropic tool definition"
• "I have three functions for my agent — write their tool schemas so the model picks the right one"
• "Document this existing endpoint as a tool the agent can consume, with required fields"

Requests like these belong to a different skill, so it shouldn't answer them:

• "Design the control loop for my tool-using agent — stop conditions and retries"
• "Split this workflow across an orchestrator and specialist subagents"
• "Draft the OpenAPI contract for our new public REST API"

If another skill answers instead, ask for this one by name: "use tool-use-schema-writer".

Check what you get

A good result:

• Descriptions are decision conditions, not function names restated. "Gets the weather" is not a description — "Returns the current temperature and conditions for a given city. Call this when the user asks about current weather, not forecasts." is.
• Required arrays are never omitted. An omitted required array means all fields are optional — the model will skip fields the function actually needs and the call will fail at runtime.
• Enum values always have descriptions. "enum": ["asc", "desc"] without a description leaves the model guessing which to use.

Next

• SKILL.md, the instructions the agent reads
• Its page on the site
• Related: agent-loop-design, subagent-design

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