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 zhaono1/agent-playbook --skill api-designergit clone --depth 1 https://github.com/zhaono1/agent-playbookWrote 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/zhaono1/agent-playbook/api-designer)<a href="https://agentmods.dev/skills/zhaono1/agent-playbook/api-designer"><img src="https://agentmods.dev/badge/skills/zhaono1/agent-playbook/api-designer/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/zhaono1/agent-playbook/api-designer"><img src="https://agentmods.dev/badge/skills/zhaono1/agent-playbook/api-designer.svg" alt="Reviewed on agentmods" width="80" height="20"></a>- Socket pass
- Snyk pass
- NVIDIA SkillSpector warn
SkillSpector: 1 finding, up to high
These are SkillSpector’s own severities. On a checked sample its high-severity flags on skills were ~96% false positives — a documented command, a public API, a “never do X” rule — so we show them as a caution to read, not a verdict. Why →
- high Tool Misuse · line 38 Tool parameters are crafted to achieve unintended or unsafe behavior. Parameter abuse can bypass intended safety checks (e.g. shell=True, --force, dangerous glob patterns).Fix: Validate all tool parameters against an allowlist. Reject dangerous parameter values (shell=True, --force, -rf /) and use safe defaults.
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 | $0.00027 | $0.01340 |
| Opus 5.5 | $0.00011 | $0.00536 |
| Sonnet 5.5 | $0.00005 | $0.00268 |
| Haiku 4.5 | $0.00003 | $0.00134 |
Grade A, and why
api-designer 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 — 242 lines — stays where its author put it; the contents beside it link to each section on GitHub.
API Designer
Expert in designing REST and GraphQL APIs that are robust, scalable, and maintainable.
When This Skill Activates
Activates when you:
- Design a new API
- Review API design
- Improve existing API
- Create API specifications
REST API Design Principles
1. Resource-Oriented Design
Good:
GET /users # List users
POST /users # Create user
GET /users/{id} # Get specific user
PATCH /users/{id} # Update user
DELETE /users/{id} # Delete user
Avoid:
POST /getUsers # Should be GET
POST /users/create # Redundant
GET /users/get/{id} # Redundant
2. HTTP Methods
| Method | Safe | Idempotent | Purpose |
|---|---|---|---|
| GET | ✓ | ✓ | Read resource |
| POST | ✗ | ✗ | Create resource |
| PUT | ✗ | ✓ | Replace resource |
| PATCH | ✗ | ✗ | Update resource |
| DELETE | ✗ | ✓ | Delete resource |
3. Status Codes
| Code | Meaning | Usage |
|---|---|---|
| 200 | OK | Successful GET, PATCH, DELETE |
| 201 | Created | Successful POST |
| 204 | No Content | Successful DELETE with no body |
| 400 | Bad Request | Invalid input |
| 401 | Unauthorized | Missing or invalid auth |
| 403 | Forbidden | Authenticated but not authorized |
| 404 | Not Found | Resource doesn't exist |
| 409 | Conflict | Resource already exists |
| 422 | Unprocessable | Valid syntax but semantic errors |
| 429 | Too Many Requests | Rate limit exceeded |
| 500 | Internal Server Error | Server error |
4. Naming Conventions
- URLs: kebab-case (
/user-preferences) - JSON: camelCase (
{"userId": "123"}) - Query params: snake_case or camelCase (
?page_size=10)
5. Pagination
GET /users?page=1&page_size=20
Response:
{
"data": [...],
"pagination": {
"page": 1,
"page_size": 20,
"total": 100,
"total_pages": 5
}
}
6. Filtering and Sorting
GET /users?status=active&sort=-created_at,name
# -created_at = descending
# name = ascending
What ships with it
5 files 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 First seen · 242 lines · 27 tokens per session scan A 9c171d474bfa
api-designer is a skill published in the GitHub repository zhaono1/agent-playbook (85 stars, last pushed 1mo ago), licensed MIT. It adds 27 tokens to every session and 1,340 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.
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