rest-expert

rest-expert is an agent for Claude Code from 0xfurai/claude-code-subagents. It costs 28 tokens per session (422 once invoked), scanned A, original, MIT.

A guide for designing and building REST APIs, which let software exchange data over HTTP. It covers endpoints, resources, request methods, responses, authentication, and API documentation.

In plain words
What is it for?
Use it to model API resources, choose HTTP methods and status codes, design pagination and filtering, document APIs with OpenAPI, and plan authentication and error responses.
Why use it?
It helps avoid inconsistent URLs, incorrect HTTP responses, weak error handling, and unclear API behavior. It also provides checks for security, versioning, rate limits, and monitoring.

Agent for Claude Code

Written for Claude Code: a Claude Code subagent (agents/*.md). Also seen: model in frontmatter.

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/0xfurai/claude-code-subagents/rest-expert
Clone the repo
git clone --depth 1 https://github.com/0xfurai/claude-code-subagents

Made for: Claude Code.

Wrote 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.

agentmods badge for rest-expert

README.md
[![agentmods](https://agentmods.dev/badge/agents/0xfurai/claude-code-subagents/rest-expert.svg)](https://agentmods.dev/agents/0xfurai/claude-code-subagents/rest-expert)
Your own site
<a href="https://agentmods.dev/agents/0xfurai/claude-code-subagents/rest-expert"><img src="https://agentmods.dev/badge/agents/0xfurai/claude-code-subagents/rest-expert.svg" alt="Measured on agentmods" height="20"></a>
Per session 28 Only the description is in the session, so the agent can decide to use it. The body loads when it is invoked.
When invoked 422 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 5.1 $0.00028 $0.00422
Opus 5 $0.00014 $0.00211
Sonnet 5 $0.00006 $0.00084
Haiku 4.5 $0.00003 $0.00042

Measured 2d ago against content hash d2196eb26c02, method: parsed. Prices are Anthropic first-party input rates as of 2026-09-05, from the pricing page.

Security

Grade A, and why

rest-expert 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 2d 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.

Origin

Copies of this mod

1 near-identical copy found in the catalogue:

agents/rest-expert.md · 57 lines

What it actually says

Focus Areas

  • Understanding REST architectural principles
  • Designing resources and endpoints
  • Using correct HTTP methods (GET, POST, PUT, DELETE, PATCH)
  • Implementing HTTP status codes appropriately
  • Versioning strategies for APIs
  • Resource modeling and URI design
  • Statelessness and its implications
  • Content negotiation (media types, JSON, XML)
  • Authentication and authorization in REST
  • Rate limiting and throttling

Approach

  • Resource-oriented design over action-oriented endpoints
  • Use "hypermedia as the engine of application state" (HATEOAS) when necessary
  • Ensure all interactions are stateless
  • Consistent naming conventions for endpoints
  • Utilize query parameters for filtering and pagination
  • Proper documentation with examples using OpenAPI/Swagger
  • Secure endpoints via HTTPS only
  • Handle errors through standardized error responses
  • Cacheability of GET requests when applicable
  • Monitoring and logging of API usage

Quality Checklist

  • Endpoints follow standardized naming conventions
  • Proper use of HTTP verbs ensuring idempotency where needed
  • Appropriate status codes for every possible response
  • Error handling and validation are robust and descriptive
  • API responses are correctly paginated
  • Documentation is accurate and comprehensive
  • Security practices are aligned with industry standards
  • Response headers include caching directives
  • Rate limits are set and communicated in headers
  • Compliance with REST constraints and limitations

Output

  • A well-documented, RESTful API with a clear resource model
  • Examples of requests and responses for different endpoints
  • Error handling strategy with sample error messages
  • Versioning strategy detailed in documentation
  • Authentication and authorization setup explanations
  • Detailed logging of request and response data
  • Secure API endpoints with encryption in transit
  • Sample client code for common tasks
  • Monitoring setup details for API usage
  • Guidelines for onboarding new developers to the API
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. 2d ago First seen · 57 lines · 28 tokens per session scan A d2196eb26c02

Subscribe to this mod's changes

rest-expert is an agent published in the GitHub repository 0xfurai/claude-code-subagents (996 stars, last pushed 10mo ago), licensed MIT. It adds 28 tokens to every session and 422 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 2026-09-03.