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`src/tool.rs` — the `Tool` trait and its entourage

The definition of “a tool” plus everything a tool produces and receives. (~2,300 lines with docs/tests.)

Key items

  • Tool — required: name, description, schema, call. Provided: is_concurrency_safe (false), is_safe_for_concurrent_execution(input), resource_key (None), is_read_only (false), system_prompt (None).
  • ToolSchema { tool, description, input_schema } — the name field is tool; JSON Schema Draft 07; serialized into requests verbatim.
  • ToolOutput — success/error/text/error_text/structured/with_hint/with_payload/structured_as; is_error is the soft-failure flag.
  • ToolError — NotFound, InvalidInput, Execution, Permission, FileNotFound, Timeout, Cancelled, Io, Json; not_found(tool, available) with the capped list.
  • ToolContext { cwd, session_id, temp_dir, is_non_interactive, user_context, extensions } — typed extensions via set_extension/get_extension.
  • DisplayHint — Text/Diff/Json/Code/Suppress/Markdown; advisory only; never affects loop semantics.
  • ToolDispatchResult — what the engine/pipeline produce per call: id, output, is_error, duration, resolved name, hint; constructors and builders.

Behavior notes

  • Tools must be cancellation-safe: futures are dropped mid-call on cancel.
  • Engine-built contexts carry the per-session temp dir (cleaned on loop drop); hosts needing durable dirs must use extensions, never temp_dir.

Deep dive: Tools.