ECC is a toolkit that organizes and improves how coding agents work through skills, memory, security checks, research practices, and related extensions. It is for developers using agents such as Claude Code, Codex, OpenCode, and Cursor.
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 affaan-m/ECC --skill api-designgit clone --depth 1 https://github.com/affaan-m/ECCWrote 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/affaan-m/ecc/api-design)<a href="https://agentmods.dev/skills/affaan-m/ecc/api-design"><img src="https://agentmods.dev/badge/skills/affaan-m/ecc/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/affaan-m/ecc/api-design"><img src="https://agentmods.dev/badge/skills/affaan-m/ecc/api-design.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 30 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 | $0.00051 | $0.03342 |
| Opus 5.5 | $0.00020 | $0.01337 |
| Sonnet 5.5 | $0.00010 | $0.00668 |
| Haiku 4.5 | $0.00005 | $0.00334 |
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 28d 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.
Copies of this mod
8 near-identical copies found in the catalogue:
- api-design — 100% identical, 1 lines differ
- api-design — 98% identical, 6 lines differ
- api-design — 97% identical, 4 lines differ
- api-design — 97% identical, 4 lines differ
- api-design — 97% identical, 4 lines differ
- api-design — 97% identical, 4 lines differ
- imlazy-api-design — 97% identical, 5 lines differ
- api-design — 97% identical, 4 lines differ
How it starts
The opening of the file, as written. The whole thing — 524 lines — stays where its author put it; the contents beside it link to each section on GitHub.
API Design Patterns
Conventions and best practices for designing consistent, developer-friendly REST APIs.
When to Activate
- Designing new API endpoints
- Reviewing existing API contracts
- Adding pagination, filtering, or sorting
- Implementing error handling for APIs
- Planning API versioning strategy
- Building public or partner-facing APIs
Resource Design
URL Structure
# Resources are nouns, plural, lowercase, kebab-case
GET /api/v1/users
GET /api/v1/users/:id
POST /api/v1/users
PUT /api/v1/users/:id
PATCH /api/v1/users/:id
DELETE /api/v1/users/:id
# Sub-resources for relationships
GET /api/v1/users/:id/orders
POST /api/v1/users/:id/orders
# Actions that don't map to CRUD (use verbs sparingly)
POST /api/v1/orders/:id/cancel
POST /api/v1/auth/login
POST /api/v1/auth/refresh
Naming Rules
# GOOD
/api/v1/team-members # kebab-case for multi-word resources
/api/v1/orders?status=active # query params for filtering
/api/v1/users/123/orders # nested resources for ownership
# BAD
/api/v1/getUsers # verb in URL
/api/v1/user # singular (use plural)
/api/v1/team_members # snake_case in URLs
/api/v1/users/123/getOrders # verb in nested resource
HTTP Methods and Status Codes
Method Semantics
| Method | Idempotent | Safe | Use For |
|---|---|---|---|
| GET | Yes | Yes | Retrieve resources |
| POST | No | No | Create resources, trigger actions |
| PUT | Yes | No | Full replacement of a resource |
| PATCH | No* | No | Partial update of a resource |
| DELETE | Yes | No | Remove a resource |
*PATCH can be made idempotent with proper implementation
Status Code Reference
# Success
200 OK — GET, PUT, PATCH (with response body)
201 Created — POST (include Location header)
204 No Content — DELETE, PUT (no response body)
# Client Errors
400 Bad Request — Validation failure, malformed JSON
401 Unauthorized — Missing or invalid authentication
403 Forbidden — Authenticated but not authorized
404 Not Found — Resource doesn't exist
409 Conflict — Duplicate entry, state conflict
422 Unprocessable Entity — Semantically invalid (valid JSON, bad data)
429 Too Many Requests — Rate limit exceeded
# Server Errors
500 Internal Server Error — Unexpected failure (never expose details)
502 Bad Gateway — Upstream service failed
503 Service Unavailable — Temporary overload, include Retry-After
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.
- 28d ago Changed · +1 lines 5568a8b1e2e9
- 1mo ago First seen · 523 lines · 51 tokens per session scan A 3d6b2d9955ed
api-design is a skill published in the GitHub repository affaan-m/ECC (281,495 stars, last pushed yesterday), licensed MIT. It adds 51 tokens to every session and 3,342 once invoked, about $0.0002 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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