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 decebals/claude-code-java --skill api-contract-reviewgit clone --depth 1 https://github.com/decebals/claude-code-javaWrote 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/decebals/claude-code-java/api-contract-review)<a href="https://agentmods.dev/skills/decebals/claude-code-java/api-contract-review"><img src="https://agentmods.dev/badge/skills/decebals/claude-code-java/api-contract-review/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/decebals/claude-code-java/api-contract-review"><img src="https://agentmods.dev/badge/skills/decebals/claude-code-java/api-contract-review.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 | $0.00044 | $0.02628 |
| Opus 5.5 | $0.00018 | $0.01051 |
| Sonnet 5.5 | $0.00009 | $0.00526 |
| Haiku 4.5 | $0.00004 | $0.00263 |
Grade A, and why
api-contract-review 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 — 380 lines — stays where its author put it; the contents beside it link to each section on GitHub.
API Contract Review Skill
Audit REST API design for correctness, consistency, and compatibility.
When to Use
- User asks "review this API" / "check REST endpoints"
- Before releasing API changes
- Reviewing PR with controller changes
- Checking backward compatibility
Quick Reference: Common Issues
| Issue | Symptom | Impact |
|---|---|---|
| Wrong HTTP verb | POST for idempotent operation | Confusion, caching issues |
| Missing versioning | /users instead of /v1/users |
Breaking changes affect all clients |
| Entity leak | JPA entity in response | Exposes internals, N+1 risk |
| 200 with error | {"status": 200, "error": "..."} |
Breaks error handling |
| Inconsistent naming | /getUsers vs /users |
Hard to learn API |
HTTP Verb Semantics
Verb Selection Guide
| Verb | Use For | Idempotent | Safe | Request Body |
|---|---|---|---|---|
| GET | Retrieve resource | Yes | Yes | No |
| POST | Create new resource | No | No | Yes |
| PUT | Replace entire resource | Yes | No | Yes |
| PATCH | Partial update | No* | No | Yes |
| DELETE | Remove resource | Yes | No | Optional |
*PATCH can be idempotent depending on implementation
Common Mistakes
// ❌ POST for retrieval
@PostMapping("/users/search")
public List<User> searchUsers(@RequestBody SearchCriteria criteria) { }
// ✅ GET with query params (or POST only if criteria is very complex)
@GetMapping("/users")
public List<User> searchUsers(
@RequestParam String name,
@RequestParam(required = false) String email) { }
// ❌ GET for state change
@GetMapping("/users/{id}/activate")
public void activateUser(@PathVariable Long id) { }
// ✅ POST or PATCH for state change
@PostMapping("/users/{id}/activate")
public ResponseEntity<Void> activateUser(@PathVariable Long id) { }
// ❌ POST for idempotent update
@PostMapping("/users/{id}")
public User updateUser(@PathVariable Long id, @RequestBody UserDto dto) { }
// ✅ PUT for full replacement, PATCH for partial
@PutMapping("/users/{id}")
public User replaceUser(@PathVariable Long id, @RequestBody UserDto dto) { }
@PatchMapping("/users/{id}")
public User updateUser(@PathVariable Long id, @RequestBody UserPatchDto dto) { }
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 First seen · 380 lines · 44 tokens per session scan A 399304f39dd1
api-contract-review is a skill published in the GitHub repository decebals/claude-code-java (754 stars, last pushed 1mo ago), licensed MIT. It adds 44 tokens to every session and 2,628 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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