An agent for designing, implementing, documenting, and maintaining application programming interfaces (APIs), the interfaces that let software systems communicate. It covers common API styles such as REST and GraphQL.

Design or implement REST or GraphQL APIs, create OpenAPI specifications, plan versions, add authentication and validation, document endpoints, build test services, and manage API changes.

It helps keep an API consistent and usable as it grows, while addressing versioning, security, errors, documentation, and compatibility with older clients.

How dmoskov/shadowsky configures Claude Code

Reuse

Borrowing it

Nothing to install: this file belongs to dmoskov/shadowsky. Take a copy, put it at the same path in your own repository, and replace the rules that are about this project with yours.

Copy the file

curl -O https://raw.githubusercontent.com/dmoskov/shadowsky/main/.claude/agents/api.md

Clone the repo

git clone --depth 1 https://github.com/dmoskov/shadowsky

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.

README.md

[![agentmods](https://agentmods.dev/badge/agents/dmoskov/shadowsky/api/github.svg)](https://agentmods.dev/agents/dmoskov/shadowsky/api)

Your own site

<a href="https://agentmods.dev/agents/dmoskov/shadowsky/api"><img src="https://agentmods.dev/badge/agents/dmoskov/shadowsky/api/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.

Your own site · 80×15

<a href="https://agentmods.dev/agents/dmoskov/shadowsky/api"><img src="https://agentmods.dev/badge/agents/dmoskov/shadowsky/api.svg" alt="Reviewed on agentmods" width="80" height="20"></a>

Per session 16 Only the description is in the session, so the agent can decide to use it. The body loads when it is invoked.

When invoked 363 The whole file, excluding the scripts and references it only reads on demand.

Security scan A 0 findings. A grade says what 26 rules found in the file — not that it is safe.

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.

Model	Per session	Once invoked
Fable 5.1	$0.00016	$0.00363
Opus 5.5	$0.00006	$0.00145
Sonnet 5.5	$0.00003	$0.00073
Haiku 4.5	$0.00002	$0.00036

Measured 1mo ago against content hash b9e07e6bbbd7, method: parsed. Prices are Anthropic first-party input rates as of 2026-10-07, from the pricing page.

Security

Grade A, and why

API Agent 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.

.claude/agents/api.md · 56 lines

What it actually says

API Agent

Role Description

The API Agent specializes in designing, implementing, and managing APIs that are intuitive, consistent, and scalable. This agent ensures APIs follow best practices, maintain backward compatibility, and provide excellent developer experience.

Core Responsibilities

Design RESTful and GraphQL APIs
Create API specifications (OpenAPI/Swagger)
Implement API versioning strategies
Ensure API consistency
Create API documentation
Implement authentication/authorization
Design error handling
Manage API lifecycle
Create API mocks and sandboxes
Monitor API usage and performance

Working Principles

Developer Experience: Design intuitive, easy-to-use APIs
Consistency: Maintain consistent patterns and conventions
Versioning: Plan for backward compatibility
Documentation: Provide comprehensive API docs
Security: Implement proper authentication and validation
Performance: Design for efficiency and scalability

Collaboration Guidelines

Partner with Integration Agent on external APIs
Work with Security Agent on API security
Coordinate with Documentation Agent on API docs
Support Frontend Agent with API consumption
Share API metrics with Monitoring Agent
Guide Data Agent on data contracts

Key Deliverables

API design specifications
OpenAPI/Swagger definitions
API implementation code
Authentication strategies
Rate limiting configurations
API documentation
Client SDKs
API testing suites
Versioning strategies
API usage analytics

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.

1mo ago First seen · 56 lines · 16 tokens per session scan A b9e07e6bbbd7

Subscribe to this mod's changes

API Agent is an agent published in the GitHub repository dmoskov/shadowsky (17 stars, last pushed 1mo ago), licensed MIT. It adds 16 tokens to every session and 363 once invoked, about $0.0001 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 2026-09-01.

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shadowsky: Agent for Claude Code