Hmbown/CodeWhale is an open-source coding agent that runs in the terminal and is written in Rust. Developers use it to inspect repositories, edit files, run commands, and coordinate work with configurable model providers, skills, MCP servers, and approval controls; the catalogue entries extend its available workflows.
Getting it into your agent
One page per mod, every tool's command on it. A separate URL per tool would split the same page into five that compete with each other.
npx skills add Hmbown/CodeWhale --skill mcp-buildergit clone --depth 1 https://github.com/Hmbown/CodeWhaleWrote this? Show the measurements
A badge with what this costs and how it scanned, read live from this page, so it follows the numbers instead of freezing them. Markdown for a README, HTML for a documentation site or a project page.
[](https://agentmods.dev/skills/hmbown/codewhale/mcp-builder)<a href="https://agentmods.dev/skills/hmbown/codewhale/mcp-builder"><img src="https://agentmods.dev/badge/skills/hmbown/codewhale/mcp-builder/github.svg" alt="Measured on agentmods" height="20"></a>Or the 80×15 button, for a site that already has a row of RSS and ATOM ones. Only the verdict fits; the numbers stay here.
<a href="https://agentmods.dev/skills/hmbown/codewhale/mcp-builder"><img src="https://agentmods.dev/badge/skills/hmbown/codewhale/mcp-builder.svg" alt="Reviewed on agentmods" width="80" height="20"></a>- Snyk pass
- NVIDIA SkillSpector pass
What it costs to keep this loaded
Counted locally with the o200k_base tokenizer, which is exact for GPT models; Claude uses its own tokenizer and its counts differ. Treat this as one consistent yardstick across the catalogue rather than a bill. Prices are per million input tokens.
| Model | Per session | Once invoked |
|---|---|---|
| Fable 5.1 | $0.00030 | $0.00366 |
| Opus 5.5 | $0.00012 | $0.00146 |
| Sonnet 5.5 | $0.00006 | $0.00073 |
| Haiku 4.5 | $0.00003 | $0.00037 |
Grade A, and why
mcp-builder scanned grade A with 0 findings against 26 rules in 11 categories — prompt injection, anti-refusal, data exfiltration, privilege escalation, supply chain, agent snooping, system-prompt leakage, SSRF and excessive agency — measured 1mo ago.
A static scan of the body, not an audit. Every finding is printed with the line that produced it so you can judge whether it matters here. A mod is markdown that instructs an agent; that is exactly why what it instructs is worth reading.
Nothing flagged
None of the 26 patterns this scan looks for appear in this file: no shell pipes, no recursive deletes, no credential paths, no hidden text, no instruction-override or anti-refusal phrasing, no agent-config snooping. That is not a guarantee, it is the absence of the things that are checkable.
What it actually says
MCP Builder
Use this skill when the user asks to create, configure, or debug an MCP server or tool integration.
Design Rules
- Prefer stdio MCP servers for local tools and HTTP/SSE for remote services.
- Keep tool schemas small, typed, and explicit. Return structured JSON where possible.
- Put secrets in environment variables, never in committed config.
- For HTTP/SSE clients, send
Accept: application/json, text/event-streamby default unless the server explicitly requires something else. - Add timeouts and clear error messages around external APIs.
Codewhale Setup
Common commands:
codewhale mcp init
codewhale mcp add my-server --command node --arg server.js
codewhale mcp add remote-server --url http://127.0.0.1:3000/mcp
codewhale mcp list
codewhale mcp validate
codewhale mcp tools
HTTP/SSE entries can include per-server headers in ~/.codewhale/mcp.json when
credentials or custom routing headers are required.
Workflow
- Define the service boundary and the minimum useful tools.
- Choose transport and credential handling.
- Implement the server using a maintained MCP SDK when available.
- Add the server with
codewhale mcp addor edit~/.codewhale/mcp.json. - Run
codewhale mcp validate, thencodewhale mcp tools. - Test one happy path and one failure path before calling it done.
What this file has done since we first saw it
Hashed on every crawl. A supply-chain change to an agent config is a question of when, not whether, so the history is kept rather than the latest state alone.
- 1mo ago First seen · 45 lines · 30 tokens per session scan A 49cff44bc429
mcp-builder is a skill published in the GitHub repository Hmbown/CodeWhale (41,099 stars, last pushed 2d ago), licensed MIT. It adds 30 tokens to every session and 366 once invoked, about $0.0001 per session on Opus 5.5. A static security scan graded it A with 0 findings. No closer match exists in the catalogue, so it is treated as the original; first seen 2026-08-30.
Other skills, from other repositories
cw-gates
Use before claiming any Codewhale change is done, green, or ready to land: the focused-to-broad verification ladder, the budget checks CI enforces, and the rules for what counts as a passing test.
cw-land
Use when turning verified Codewhale work into commits, branches, or a merge: choosing direct-main vs. worktree vs. integration branch, preserving contributor credit, and honoring the gate artifact before merging.
cw-slice
Use before writing code for any Codewhale feature, upgrade, or refactor: find the existing owner of the behavior, bound the change to one reviewable slice, and fix the evidence bar before you start.
cw-dogfood
Use when a Codewhale change needs proving in the real product, or when asked to build/install/dogfood the local binaries: stamped release build, atomic install, fresh-shell verification, and the manual QA that gates cannot cover.
cw-handoff
Use when writing a Codewhale takeover prompt, continuation note, or end-of-session summary for another agent or a later session: a paste-ready handoff grounded in live state, with done/suspected/blocked kept separate.
cw-orient
Use at the start of any Codewhale work session, or when unsure which checkout, branch, or worktree is authoritative: establish live repo truth before reading a plan or editing a file.