codewhale/docs/TOOL_SURFACE.md

Tool surface

Why these specific tools, in this groupings, and how each one is meant to be chosen over the available shell equivalent. Companion to crates/tui/src/prompts/agent.txt.

Design stance

• Dedicated tools over exec_shell whenever the dedicated tool returns structured output. Bash escaping is error-prone and platform behavior varies (GNU vs BSD grep, rg is not always installed). Structured output also frees the model from re-parsing free-form text.
• exec_shell for everything else. Build, test, format, lint, ad-hoc commands, anything platform-specific. We don't try to wrap the long tail.
• Drop tools that don't beat their shell equivalent. Two-tool aliases for the same backing operation are a model trap — the LLM will alternate between them and the cache hit rate suffers.

Final surface (v0.5.1)

File operations

Tool	Niche
read_file	Read a UTF-8 file. PDFs auto-extracted via pdftotext (poppler) when available; pages: "1-5" slices large docs.
list_dir	Structured, gitignore-aware listing. Preferred over exec_shell("ls").
write_file	Create or overwrite a file.
edit_file	Search-and-replace inside a single file. Cheaper than a full rewrite.
apply_patch	Apply a unified diff. The right tool for multi-hunk edits.

Search

Tool	Niche
grep_files	Regex search file contents within the workspace; structured matches + context lines. Pure-Rust (regex crate), no rg/grep shell-out.
file_search	Fuzzy-match filenames (not contents). Use when you know roughly the name.
web_search	DuckDuckGo (with Bing fallback); ranked snippets + ref_id for citation.
fetch_url	Direct HTTP GET on a known URL. Faster than web_search when the link is already known. HTML stripped to text by default.

Shell

Tool	Niche
exec_shell	Run a shell command. Foreground or background (background: true returns a task_id).
exec_shell_wait	Poll a background task for incremental output.
exec_shell_interact	Send stdin to a running background task and read incremental output.

Git / diagnostics / testing

Tool	Niche
git_status	Inspect repo status without running shell.
git_diff	Inspect working-tree or staged diffs.
diagnostics	Workspace, git, sandbox, and toolchain info in one call.
run_tests	cargo test with optional args.

Task management

Tool	Niche
todo_write	Granular per-item progress.
update_plan	Structured checklist for complex multi-step work.
note	One-off important fact for later.

Sub-agents

agent_spawn, agent_swarm, spawn_agents_on_csv, plus the supporting tools (agent_result / swarm_result / wait / send_input / agent_assign / agent_cancel / resume_agent / agent_list / report_agent_job_result / swarm_status). See agent.txt for the delegation protocol.

Recently consolidated (v0.5.1)

Removed from the prompt as duplicates of equivalent tools (the underlying dispatchers still resolve them, so existing sessions don't break — they just no longer pollute the model's tool list):

• spawn_agent → use agent_spawn.
• close_agent → use agent_cancel.
• assign_agent → use agent_assign.

Why we don't ship a single bash tool

Single-bash agents (Claude Code's design) are powerful but hand the model all the foot-guns of shell scripting: quoting, platform divergence, side-effects from misread cwd, cd not persisting between calls, etc. Our file tools are also significantly cheaper to render in the transcript (structured JSON-shaped output collapses better than ls -la walls of text).

The model can always fall back to exec_shell when something is missing. The dedicated tools just take the common 80% off the shell escape-hatch.