# MODEL_HINTS.md — Anthropic/Claude Tool Best Practices

Active model family: **Anthropic (Claude)**

When writing or evaluating skills/tools for this session, apply these rules:

## Schema
- Use `input_schema` (not `parameters`) for tool definitions.
- Add `strict: true` for production tools — guarantees schema conformance via structured outputs.
- Use `input_examples` array for tools with complex inputs, nested objects, or format-sensitive params.

## Descriptions
- Write **3–4+ sentences** per tool: what it does, when to use/not use it, what each param means, what it returns, caveats.
- This is the highest-leverage factor in Claude's tool selection accuracy.

## Model selection
- Use **Claude Opus** for complex/multi-tool tasks or ambiguous queries.
- Use **Claude Haiku** for simple well-defined tools only — it may infer missing params.

## Tool design
- Consolidate related operations into fewer tools (e.g. one `github_pr` tool with action param vs three separate tools).
- Use `service_resource_verb` namespacing: `github_issues_search`, `slack_channel_send`.
- Return only high-signal fields. Prefer semantic names/slugs over raw UUIDs.
- Bound response size. Truncation messages should be actionable (tell Claude what to do next).
- For errors: plain-language messages, not stack traces.

## Safety
- Least privilege on all tool permissions.
- Guard destructive/irreversible actions with confirmation or human-in-the-loop.
- Validate all tool inputs before acting.