headcount is an organization of independently installable Claude Code plugins, each grouping skills for a department such as finance, security, or demand generation. Claude Code users install the departments they need and invoke their skills for specialized work; the catalogue entries are skills and related agent tooling from that organization.
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 cbrock84/headcount --skill api-designgit clone --depth 1 https://github.com/cbrock84/headcountWrote 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/cbrock84/headcount/api-design)<a href="https://agentmods.dev/skills/cbrock84/headcount/api-design"><img src="https://agentmods.dev/badge/skills/cbrock84/headcount/api-design/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/cbrock84/headcount/api-design"><img src="https://agentmods.dev/badge/skills/cbrock84/headcount/api-design.svg" alt="Reviewed on agentmods" width="80" height="20"></a>- 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 | $0.00064 | $0.00760 |
| Opus 5.5 | $0.00026 | $0.00304 |
| Sonnet 5.5 | $0.00013 | $0.00152 |
| Haiku 4.5 | $0.00006 | $0.00076 |
Grade A, and why
api-design 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.
How it starts
The opening of the file, as written. The whole thing — 79 lines — stays where its author put it; the contents beside it link to each section on GitHub.
API design
An API is a promise you cannot withdraw once someone depends on it. Design accordingly: the cost of getting it wrong is paid continuously by everyone who integrates.
Model the domain, not the database
Expose concepts the consumer thinks in. An interface that mirrors internal table structure leaks implementation, breaks whenever storage changes, and forces consumers to reconstruct meaning you already had.
Name things as the domain names them. Consistency in naming, casing, date formats and identifier style matters more than any individual choice being optimal — an interface that is uniformly imperfect is learnable, and one that is inconsistently excellent is not.
Errors are part of the contract
Most integrations spend most of their code on failure. Give it the same care as the success path:
- Distinguish machine-readable code from human-readable message. Consumers branch on the code; the message is for the developer reading logs.
- Say what to do about it. Retryable or not, and after how long.
- Never leak internals — stack traces and SQL in error bodies are a security finding as well as bad design.
- Be consistent about which failures are which status. Validation, authorization, and conflict are different situations and should never share a shape.
Compatibility
Adding an optional field is safe. Removing a field, renaming one, tightening validation, changing a default, or adding a required parameter are all breaking, and the last three break consumers who are doing nothing wrong.
Version when you must break, and be explicit about how long the previous version lives. A deprecation without a date is a deprecation nobody acts on.
Prefer expansion over versioning where possible: a new optional field costs a consumer nothing, a new version costs them a migration.
Pagination, filtering and limits
Any collection that can grow needs pagination from the first release — retrofitting it is a breaking change to every consumer. Prefer cursors over offsets for anything that changes while being read; offset pagination silently skips and duplicates records under concurrent writes.
What ships with it
1 file beside SKILL.md in the same directory: the scripts, references and assets a skill reads on demand. Not counted in the per-session cost; read them before you install if any of them is executable.
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 Changed · +7 lines c2da55f2fd7d
- 1mo ago First seen · 72 lines · 64 tokens per session scan A 57f093489298
api-design is a skill published in the GitHub repository cbrock84/headcount (2,077 stars, last pushed 2d ago), licensed MIT. It adds 64 tokens to every session and 760 once invoked, about $0.0003 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 2026-09-03.
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