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Agent skill

Backend API Design

by c0x12c in c0x12c/ai-toolkit

Design RPC-style APIs with layered architecture (Controller → Manager → Repository).

No licenceAuto-check passedBackend & APIs

Install Backend API Design

skills CLI
$ npx skills add c0x12c/ai-toolkit --skill backend-api-design -a claude-code

Project install by default; add -g for ~/.claude/skills/.

GitHub CLI
$ gh skill install c0x12c/ai-toolkit backend-api-design --agent claude-code

Project scope by default; add --scope user for a personal install. Needs GitHub CLI 2.90.0 or later (public preview).

Manual copy
$ git clone --depth 1 https://github.com/c0x12c/ai-toolkit.git skills-src && mkdir -p .claude/skills && cp -r skills-src/.codex/skills/backend-api-design .claude/skills/backend-api-design && rm -rf skills-src

Use ~/.claude/skills/ instead of .claude/skills for a personal install. The folder must contain SKILL.md.

Claude Code skills documentation · loads skills from .claude/skills/

Facts

Skill name
backend-api-design
GitHub stars
106
Token cost
~814 tokens
SKILL.md length
258 words
Files
2
Skills in repo
33
Repo updated
First seen
Licence
None found

At a glance

Design RPC-style APIs with layered architecture (Controller → Manager → Repository).

  • Creating new API endpoints
  • SKILL.md covers URL Patterns, Hard Rules, Layered Architecture and Quick Code Reference, plus 1 more section
  • Instructions only: no scripts, shell commands, URLs or credentials in SKILL.md
  • Designing API contracts

What it does

Backend API Design is an agent skill from c0x12c/ai-toolkit. Design RPC-style APIs with layered architecture (Controller → Manager → Repository). Use when creating new API endpoints, designing API contracts, or reviewing API patterns.

Its SKILL.md is about 810 tokens, which your agent loads only when the skill is triggered. The skill folder holds 1 other file (for example `code-patterns.md`).

It sits in Backend & APIs, covering API design and REST APIs.

When your agent uses it

  • Creating new API endpoints
  • Designing API contracts
  • Reviewing API patterns

Example prompts

  • “/backend-api-design”

What it can do on your machine

Read from SKILL.md and the folder at commit 96b2c9d. It shows what the files ask for, not the result of running them.

  • Tool permissions

    Pre-approves nothing: there is no allowed-tools line, so your agent's usual permission prompts apply.

    From allowed-tools in the SKILL.md frontmatter.

  • Runs code

    No scripts in the folder and no shell commands in SKILL.md (its code samples are kotlin).

    From the folder's file list and the shell code blocks in SKILL.md.

  • Network

    No URLs in SKILL.md.

    From URLs in SKILL.md, links to its own repository left out.

  • Credentials

    Names no API keys, tokens, secrets or passwords.

    From names ending in _API_KEY, _TOKEN, _SECRET, _KEY or _PASSWORD in SKILL.md.

Context cost

Backend API Design loads about 814 tokens when it runs. Until then it costs about 48 tokens; SKILL.md has 258 words of instructions outside code blocks.

Always · name and description, kept in context so the agent knows when to use it
~48
When it runs · the whole SKILL.md, loaded when a task matches
~814

Estimates: characters ÷ 4, the usual rule of thumb; real counts depend on the model's tokenizer. Scripts and assets cost tokens only if the agent reads them.

Safety

Auto-check passed

The automated check found no risky patterns in SKILL.md.

Automated static check — not a guarantee. Review scripts before installing. It scans the text of SKILL.md for risky patterns (piping downloads into a shell, reading credential files, hidden Unicode, destructive commands); files beside SKILL.md are not scanned.

SKILL.md

Without a licence we can't republish the file, so here is its outline and opening line. It has 258 words (~814 tokens).

name
backend-api-design

Read the full SKILL.md on GitHub

Files

SKILL.md and 1 other file in .codex/skills/backend-api-design of c0x12c/ai-toolkit.

  • SKILL.md
  • code-patterns.md

Open the folder on GitHubat commit 96b2c9d

Compare with similar skills

Backend API Design next to the 5 skills that share the most tags, products or categories with it. Stars are the repository's; “used in” counts other GitHub owners with a copy.

Backend API Design compared with similar skills
SkillStarsUsed inTokensAuto-checkLicenceRepo updated
Backend API Design this skillc0x12c/ai-toolkit106—~814Automated safety check: PassNone
API DesignerJeffallan/claude-skills12k2 repos~2kAutomated safety check: PassMIT
Nodejs Backend Patternsever-works/ever-works15818 repos~4kAutomated safety check: PassAGPL-3.0
Pangolin CRUD Endpointsfosrl/pangolin23k—~461Automated safety check: PassCustom licence
Old Coder API DesignAmazingAng/old-coder7491 repos~3.4kAutomated safety check: PassMIT
REST API Contract Reviewdecebals/claude-code-java7511 repos~2.8kAutomated safety check: PassMIT

Similar skills

  • API Designer

    Jeffallan/claude-skills

    Designs REST and GraphQL APIs from resource modeling to an OpenAPI 3.1 contract, with versioning, pagination and RFC 7807 error handling.

    12k GitHub starsUsed in 2 repos~2k tokens
    Backend & APIsAuto-check passed

  • Nodejs Backend Patterns

    ever-works/ever-works

    Build production-ready Node.js backend services with Express/Fastify, implementing middleware patterns, error handling, authentication, database integration, and API design best practices.

    158 GitHub starsUsed in 18 repos~4k tokens
    Backend & APIsAuto-check passed

  • Pangolin CRUD Endpoints

    fosrl/pangolin

    Use whenever asked to add, create, or scaffold a CRUD endpoint, router, or entity in this repo's server (create/list/get/update/delete handlers, new…

    23k GitHub stars~461 tokensUpdated today
    Backend & APIsAuto-check passed

  • Old Coder API Design

    AmazingAng/old-coder

    Reviews or designs an HTTP/JSON API's endpoints, auth, pagination, versioning and deprecations, guarding against inventing a bespoke interface or silently breaking consumers.

    749 GitHub starsUsed in 1 repo~3.4k tokens
    Backend & APIsAuto-check passed

  • REST API Contract Review

    decebals/claude-code-java

    Reviews REST API design for correct HTTP verbs, versioning, DTO use, consistent responses and backward compatibility before an API change ships.

    751 GitHub starsUsed in 1 repo~2.8k tokens
    Backend & APIsAuto-check passed

  • Backend Fundamentals

    DanielPodolsky/ownyourcode

    Reviews API design, REST conventions, and backend architecture.

    290 GitHub starsUsed in 1 repo~1.1k tokens
    Backend & APIsAuto-check passed

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  • Database Table Creator

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Categories

Questions about Backend API Design

What does Backend API Design do?

Design RPC-style APIs with layered architecture (Controller → Manager → Repository). Backend API Design is an agent skill from c0x12c/ai-toolkit. Design RPC-style APIs with layered architecture (Controller → Manager → Repository).

When should I use Backend API Design?

Backend API Design fits situations like: creating new API endpoints; designing API contracts; reviewing API patterns.

How do I install Backend API Design in Claude Code?

Run `npx skills add c0x12c/ai-toolkit --skill backend-api-design -a claude-code`. Or copy the skill folder (.codex/skills/backend-api-design in c0x12c/ai-toolkit) into .claude/skills/backend-api-design in your project. Claude Code loads it when a task matches its description.

How do I install Backend API Design in Codex?

Run `npx skills add c0x12c/ai-toolkit --skill backend-api-design -a codex`. Or copy the skill folder (.codex/skills/backend-api-design in c0x12c/ai-toolkit) into .agents/skills/backend-api-design in your project. Codex loads it when a task matches its description.

Can I use Backend API Design in Cursor, Gemini CLI or GitHub Copilot?

Cursor, Gemini CLI, GitHub Copilot and OpenCode also load SKILL.md folders. With the skills CLI, run `npx skills add c0x12c/ai-toolkit --skill backend-api-design -a cursor` (or -a gemini-cli, github-copilot or opencode for the others). To copy it by hand, put the folder in .cursor/skills/backend-api-design, .gemini/skills/backend-api-design, .github/skills/backend-api-design and .opencode/skills/backend-api-design in your project.

What does Backend API Design need to run?

SKILL.md names no scripts, command-line tools or credentials: Backend API Design is instructions for the agent only.

Does Backend API Design access the network?

SKILL.md contains no URLs. Any network use would come from the scripts or tools the agent runs. This is read from the text; nothing was executed.

Is Backend API Design safe to install?

Our automated static check of SKILL.md found no risky patterns, such as piping downloads into a shell, reading credential files or hidden Unicode. It is not a guarantee. Review the folder before installing.

What licence does Backend API Design use?

No licence was found for Backend API Design or its repository. Without one, default copyright applies: ask the author before reusing or redistributing it.

How many tokens does Backend API Design use?

About 814 tokens (SKILL.md is roughly 3.3k characters). Agents keep only the skill's name and description in context until a task matches; then they load SKILL.md in full.

What are the alternatives to Backend API Design?

Skills that share tags, products or a category with Backend API Design: API Designer (Jeffallan/claude-skills, 12k stars), Nodejs Backend Patterns (ever-works/ever-works, 158 stars), Pangolin CRUD Endpoints (fosrl/pangolin, 23k stars) and Old Coder API Design (AmazingAng/old-coder, 749 stars). The comparison table on this page puts their stars, adoption, token cost, safety result and licence side by side.

Who maintains Backend API Design?

c0x12c (a GitHub organization) maintains it in c0x12c/ai-toolkit, which has 106 GitHub stars. The repository holds 33 skills in this directory. The repository was last updated on June 18, 2026.

Source: c0x12c/ai-toolkit on GitHub. Facts on this page come from the repository at the commit we read; the author's words are quoted as theirs.