LangChain Tool Builder

Helps define LangChain (Python) tools using Claude Code's buildTool() pattern: a unified class that co-locates identity, schema, security properties, and execution logic, with fail-closed defaults so new tools are safe by default.

Why this pattern matters

Claude Code enforces three things that vanilla LangChain tools lack:

1. Fail-closed defaults — is_read_only, is_destructive, is_concurrency_safe all default to False. A tool that forgets to declare its properties is conservatively treated as write-capable.
2. Layered execution — validate_semantics → check_permissions → _call are separate methods, so validation logic doesn't bleed into permission logic or business logic.
3. Self-contained definition — schema, description, security metadata, and execution all live in one class. No separate permission middleware to wire up.

Workflow

Step 1 — Install the base class