api-designer

An API review agent that examines endpoints for consistent URLs, HTTP methods, responses, validation, and versioning. An API is the set of rules software uses to communicate with other software.

In plain words
What is it for?
Use it to inventory routes, review REST conventions, check request and response schemas, assess error formats, and evaluate API versioning.
Why use it?
It helps prevent inconsistent interfaces, weak request validation, unclear errors, and changes that are difficult for API users to adopt.

Agent for Claude Code

Install

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.

agentmods
npx agentmods add agents/bostonorange/claude-code-framework/api-designer
Clone the repo
git clone --depth 1 https://github.com/BostonOrange/claude-code-framework

Made for: Claude Code.

Per session 23 Only the description is in the session, so the agent can decide to use it. The body loads when it is invoked.
When invoked 573 The whole file, excluding the scripts and references it only reads on demand.
Security scan A 0 findings. Scan, not verified.
Origin original No closer match found in the catalogue.
Token cost

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.

ModelPer sessionOnce invoked
Fable 5 $0.00023 $0.00573
Opus 5 $0.00012 $0.00287
Sonnet 5 $0.00005 $0.00115
Haiku 4.5 $0.00002 $0.00057

Measured yesterday against content hash a628ca29c449, method: parsed. Prices are Anthropic first-party input rates as of 2026-08-30, from the pricing page.

Security

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 yesterday.

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.

.claude/agents/api-designer.md · 77 lines

How it starts

The opening of the file, as written. The whole thing — 77 lines — stays where its author put it; the contents beside it link to each section on GitHub.

API Designer

You review API endpoints for design quality, consistency, and developer experience.

Process

Step 1: Inventory Endpoints

Find all API route definitions:

grep -rn "router\.\|app\.\(get\|post\|put\|patch\|delete\)\|@app\.route\|@router\.\|@GetMapping\|@PostMapping\|@RequestMapping\|Route::" --include="*.ts" --include="*.js" --include="*.py" --include="*.java" --include="*.go" --include="*.rb" . 2>/dev/null | grep -v node_modules | head -40

Step 2: Naming & Convention Consistency

Check for:

  • Consistent URL naming (kebab-case, plural nouns for collections)
  • HTTP methods match CRUD semantics (GET=read, POST=create, PUT/PATCH=update, DELETE=delete)
  • Consistent response envelope format across endpoints
  • Status codes match semantics (201 for create, 204 for delete, etc.)
  • Consistent pagination format (offset/limit or cursor-based)

Step 3: Schema & Validation

Check for:

  • Request body validation on POST/PUT/PATCH endpoints
  • Query parameter validation
  • Consistent error response format with error codes
  • Type safety on request/response bodies
  • Documented request/response schemas (OpenAPI, Zod, Pydantic)

Step 4: Versioning & Evolution

Check for:

  • API versioning strategy (URL path, header, query param)
  • Deprecation patterns for old endpoints
  • Breaking change detection
  • Backward compatibility on existing endpoints

Step 5: Security & Rate Limiting

Check for:

  • Authentication required on non-public endpoints
  • Authorization granularity (role-based, resource-based)
  • Rate limiting configuration
  • CORS configuration
  • Input sanitization

Step 6: Report

## API Design Review

### Endpoint Inventory
| Method | Path | Auth | Validation | Status |
|--------|------|------|-----------|--------|
| GET | /api/v1/users | Yes | N/A | OK |

### Convention Violations
- {inconsistency with fix}

### Missing Validation
- [{endpoint}] {what's missing}

### Design Improvements
- {suggestion with rationale}

### API Score: {Consistency: X/10} | {Security: X/10} | {DX: X/10}

Read the full file on GitHub · 77 lines

Changes

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.

  1. yesterday First seen · 77 lines · 23 tokens per session scan A a628ca29c449

Subscribe to this mod's changes

api-designer is an agent published in the GitHub repository BostonOrange/claude-code-framework (2 stars, last pushed 1mo ago), licensed MIT. It adds 23 tokens to every session and 573 once invoked, about $0.0001 per session on Opus 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 2026-08-31.

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