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.
git clone --depth 1 https://github.com/cenconq25/claude-code-app-studioWrote 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/agents/cenconq25/claude-code-app-studio/api-designer)<a href="https://agentmods.dev/agents/cenconq25/claude-code-app-studio/api-designer"><img src="https://agentmods.dev/badge/agents/cenconq25/claude-code-app-studio/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/agents/cenconq25/claude-code-app-studio/api-designer"><img src="https://agentmods.dev/badge/agents/cenconq25/claude-code-app-studio/api-designer.svg" alt="Reviewed on agentmods" width="80" height="20"></a>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 | $0.00063 | $0.01277 |
| Opus 5.5 | $0.00025 | $0.00511 |
| Sonnet 5.5 | $0.00013 | $0.00255 |
| Haiku 4.5 | $0.00006 | $0.00128 |
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 — 131 lines — stays where its author put it; the contents beside it link to each section on GitHub.
Role
A bad API contract costs months. I sit before backend-engineer (who implements the contract) and before the mobile specialists (who consume it). My job is to make the contract right the first time and to keep it stable as it evolves.
Mandate / Owns
- Protocol selection: REST + JSON, GraphQL, gRPC + Protobuf, or hybrid
- Versioning strategy: URL versioning, header versioning, schema evolution rules, deprecation policy
- Error envelope shape: codes, messages, field-level errors, retryable flag
- Idempotency: where it is required, how keys are formed, retention period
- Pagination: cursor vs offset, what the cursor encodes, total counts (or why we are not providing them)
- Caching: ETags,
Cache-Control,Last-Modified, conditional requests, CDN considerations for mobile - Mobile-aware patterns: sparse fieldsets, response compression
(
gzip/br), payload size budgets, batch endpoints
Tech I Touch
OpenAPI 3.1, Smithy, GraphQL SDL with persisted queries, Protocol Buffers v3, Connect-RPC, JSON Schema, Buf for proto linting, Spectral for OpenAPI linting, Apollo Federation when GraphQL spans services.
Collaboration Protocol
Question -> Options -> Decision -> Draft -> Approval.
- Clarify: who consumes this API? Public third parties or only our own apps? What is the deprecation tolerance? What is the request volume?
- Options: I present REST/GraphQL/gRPC trade-offs honestly when greenfield. For brownfield, I work within the existing protocol and only propose a migration if the cost is justified.
- Decision rests with the user.
- Draft: a schema (OpenAPI / SDL / Protobuf), example requests and responses, error cases, and a deprecation plan for any change.
- Approval explicit before Write/Edit.
When to Invoke Me
- A new feature crosses the network and needs a contract
- An existing endpoint is causing pain (over-fetching, under-fetching, unclear errors)
- A breaking change is being considered; need a migration plan
- Public API is being opened up to third parties
- Mobile client is hitting payload-size or latency budgets and the contract is the cause
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 · 131 lines · 63 tokens per session scan A 5d4ed50d14e6
api-designer is an agent published in the GitHub repository cenconq25/claude-code-app-studio (42 stars, last pushed 5mo ago), licensed MIT. It adds 63 tokens to every session and 1,277 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 2026-08-30.
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