api-blueprint

api-blueprint is a skill for Claude Code, Codex from nlinhvu/learn-java-frameworks-marketplace. It costs 155 tokens per session (3,451 once invoked), scanned A, original, Apache-2.0.

An analysis and planning guide that starts with the public API of a software project—the functions, classes, or endpoints users call—and traces each feature inward. It creates a buildable simplified Java project, even when the source uses another language.

In plain words
What is it for?
Use it to study a project’s API, organize features by common usage, and plan a progressive Java reimplementation.
Why use it?
It provides a learning path through an unfamiliar codebase, starting with what users can call instead of requiring you to understand the internals first. It also maps call chains and design decisions with diagrams.

Skill for Claude CodeCodex

Part of the api-learning plugin — 2 skills, 3 agents shipped together

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 skills/nlinhvu/learn-java-frameworks-marketplace/api-blueprint
Any agent
npx skills add nlinhvu/learn-java-frameworks-marketplace --skill api-blueprint
Clone the repo
git clone --depth 1 https://github.com/nlinhvu/learn-java-frameworks-marketplace

Made for: Claude Code, Codex.

Or install api-learning, the plugin that ships this one along with the rest of its 2 skills, 3 agents.

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 api-blueprint

README.md
[![agentmods](https://agentmods.dev/badge/skills/nlinhvu/learn-java-frameworks-marketplace/api-blueprint.svg)](https://agentmods.dev/skills/nlinhvu/learn-java-frameworks-marketplace/api-blueprint)
Your own site
<a href="https://agentmods.dev/skills/nlinhvu/learn-java-frameworks-marketplace/api-blueprint"><img src="https://agentmods.dev/badge/skills/nlinhvu/learn-java-frameworks-marketplace/api-blueprint.svg" alt="Measured on agentmods" height="20"></a>
Per session 155 Skills are progressive disclosure: only the name and description are preloaded; the body loads when the skill is used.
When invoked 3,451 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 $0.00155 $0.03451
Opus 5 $0.00077 $0.01725
Sonnet 5 $0.00031 $0.00690
Haiku 4.5 $0.00015 $0.00345

Measured 4d ago against content hash a4f0451d1554, method: parsed. Prices are Anthropic first-party input rates as of 2026-08-30, from the pricing page.

Security

Grade A, and why

api-blueprint 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 4d 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.

plugins/api-learning/skills/api-blueprint/SKILL.md · 280 lines

How it starts

The opening of the file, as written. The whole thing — 280 lines — stays where its author put it; the contents beside it link to each section on GitHub.

API Blueprint — API-First Learning Outline

Philosophy: Outside-In, API-First

The fastest way to learn a project's design and confidently re-implement it is to start where the user starts — the public API. Instead of hunting for the project's internal "heart" and building outward (v1 approach), this skill:

  1. Identifies the API surface — the classes, functions, endpoints, and methods that project users actually import and call in their application code (in any language)
  2. Organizes features as vertical slices — each feature represents one API capability, traced from the public method all the way down through internal layers
  3. Orders by usage tier — most commonly used APIs first, power-user/advanced APIs last
  4. Produces a simplified Java reimplementation — the output is always a buildable Java project, regardless of the source project's language
  5. Visualizes everything — Mermaid diagrams for API surface maps, call chains, learning paths, and architecture overviews with ★ Insight blocks at every design decision

This approach works because:

  • You're productive immediately — each feature gives you a working, callable Java API
  • You understand why each internal piece exists — because you traced from a concrete API call
  • You learn cross-language design patterns — seeing how Python/Go/Rust concepts map to Java
  • You see the big picture — Mermaid diagrams show how features, layers, and call chains connect

MANDATORY: Use Extended Thinking

Use extended thinking for the analysis phase. The quality of the outline depends entirely on deep upfront reasoning about the source project's API surface and internal architecture. Before writing any output:

  • Identify the source project's language and technology stack
  • Map the full public API surface and classify by usage tier (Tier 1/2/3)
  • Trace Tier 1 API call chains from the public method inward through each depth layer
  • Identify recurring depth layers across call chains and name them
  • Determine vertical slice boundaries — which API methods group into a single feature
  • Plan the usage-tier ordering and dependency flow between features
  • Plan technology mapping: source language concepts to Java equivalents

Read the full file on GitHub · 280 lines

Files

What ships with it

2 files beside SKILL.md in the same directory: the scripts, references and assets a skill reads on demand. Not counted in the per-session cost; read them before you install if any of them is executable.

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. 4d ago First seen · 280 lines · 155 tokens per session scan A a4f0451d1554

Subscribe to this mod's changes

api-blueprint is a skill published in the GitHub repository nlinhvu/learn-java-frameworks-marketplace (20 stars, last pushed 4mo ago), licensed Apache-2.0. It adds 155 tokens to every session and 3,451 once invoked, about $0.0008 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 2026-08-30.

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