Agent skill

Agent Builder

by shareAI-lab in shareAI-lab/learn-claude-code

Design and build AI agents for any domain. An agent skill from shareAI-lab/learn-claude-code.

MITAuto-check passedAI & LLM Engineering

Install Agent Builder

skills CLI
$ npx skills add shareAI-lab/learn-claude-code --skill agent-builder -a claude-code

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

GitHub CLI
$ gh skill install shareAI-lab/learn-claude-code agent-builder --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/shareAI-lab/learn-claude-code.git skills-src && mkdir -p .claude/skills && cp -r skills-src/skills/agent-builder .claude/skills/agent-builder && 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
agent-builder
GitHub stars
78k
Used in
6 other repos
Token cost
~1.2k tokens
SKILL.md length
505 words
Files
6 (incl. scripts, references)
Skills in repo
4
Repo updated
First seen
Licence
MIT

At a glance

Design and build AI agents for any domain. An agent skill from shareAI-lab/learn-claude-code.

  • Works in 3 steps: Capabilities (What can it DO?) → Knowledge (What does it KNOW?) → Context (What has happened?)
  • Ask to create an agent
  • SKILL.md covers The Core Philosophy, The Three Elements, Agent Design Thinking and Progressive Complexity, plus 5 more sections
  • Runs Python scripts from its folder

What it does

Agent Builder is an agent skill from shareAI-lab/learn-claude-code. Design and build AI agents for any domain. Use when users: (1) ask to "create an agent", "build an assistant", or "design an AI system" (2) want to understand agent architecture, agentic patterns, or autonomous AI (3) need help with capabilities, subagents, planning, or skill mechanisms (4) ask about Claude Code, Cursor, or similar agent internals (5) want to build agents for business, research, creative, or operational tasks Keywords: agent, assistant, autonomous, workflow, tool use, multi-step, orchestration

Its SKILL.md is about 1.2k tokens, which your agent loads only when the skill is triggered. The skill folder holds 7 other files, including scripts and reference files (for example `references/agent-philosophy.md`, `references/minimal-agent.py` and `references/subagent-pattern.py`).

It sits in AI & LLM Engineering, covering Building AI agents and Subagents. The repository describes itself as: Bash is all you need - A nano claude code–like 「agent harness」, built from 0 to 1. The licence is MIT.

When your agent uses it

  • Ask to create an agent
  • Build an assistant
  • Design an AI system
  • Want to understand agent architecture

Example prompts

  • “create an agent”
  • “build an assistant”
  • “design an AI system”
  • “/agent-builder”

Requirements

  • Python 3

Workflow steps

3 steps, taken from the step headings in SKILL.md.

  1. Capabilities (What can it DO?)
  2. Knowledge (What does it KNOW?)
  3. Context (What has happened?)

What it can do on your machine

Read from SKILL.md and the folder at commit ce8f9f1. 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

    Ships 1 file in scripts/ (Python), which the agent can run.

    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

Agent Builder loads about 1.2k tokens when it runs, and up to ~8.2k if it reads all its reference files. Until then it costs about 132 tokens; SKILL.md has 505 words of instructions outside code blocks.

Always · name and description, kept in context so the agent knows when to use it
~132
When it runs · the whole SKILL.md, loaded when a task matches
~1.2k
With references · SKILL.md plus every file in references/, read only if the agent opens them
~8.2k

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); the scripts in this folder are not scanned.

SKILL.md

The full file from shareAI-lab/learn-claude-code at commit ce8f9f1, republished under its MIT licence (© shareAI-lab). 505 words, ~1,179 tokens.

Download SKILL.mdSave it as .claude/skills/agent-builder/SKILL.md (or your agent's skills folder). This skill also uses 5 other files; get the full folder from GitHub.
name
agent-builder
description
Design and build AI agents for any domain. Use when users: (1) ask to "create an agent", "build an assistant", or "design an AI system" (2) want to understand agent architecture, agentic patterns, or autonomous AI (3) need help with capabilities, subagents, planning, or skill mechanisms (4) ask about Claude Code, Cursor, or similar agent internals (5) want to build agents for business, research, creative, or operational tasks Keywords: agent, assistant, autonomous, workflow, tool use, multi-step, orchestration

Agent Builder

Build AI agents for any domain - customer service, research, operations, creative work, or specialized business processes.

The Core Philosophy

The model already knows how to be an agent. Your job is to get out of the way.

An agent is not complex engineering. It's a simple loop that invites the model to act:

LOOP:
  Model sees: context + available capabilities
  Model decides: act or respond
  If act: execute capability, add result, continue
  If respond: return to user

That's it. The magic isn't in the code - it's in the model. Your code just provides the opportunity.

The Three Elements

1. Capabilities (What can it DO?)

Atomic actions the agent can perform: search, read, create, send, query, modify.

Design principle: Start with 3-5 capabilities. Add more only when the agent consistently fails because a capability is missing.

2. Knowledge (What does it KNOW?)

Domain expertise injected on-demand: policies, workflows, best practices, schemas.

Design principle: Make knowledge available, not mandatory. Load it when relevant, not upfront.

3. Context (What has happened?)

The conversation history - the thread connecting actions into coherent behavior.

Design principle: Context is precious. Isolate noisy subtasks. Truncate verbose outputs. Protect clarity.

Agent Design Thinking

Before building, understand:

  • Purpose: What should this agent accomplish?
  • Domain: What world does it operate in? (customer service, research, operations, creative...)
  • Capabilities: What 3-5 actions are essential?
  • Knowledge: What expertise does it need access to?
  • Trust: What decisions can you delegate to the model?

CRITICAL: Trust the model. Don't over-engineer. Don't pre-specify workflows. Give it capabilities and let it reason.

Progressive Complexity

Start simple. Add complexity only when real usage reveals the need:

LevelWhat to addWhen to add it
Basic3-5 capabilitiesAlways start here
PlanningProgress trackingMulti-step tasks lose coherence
SubagentsIsolated child agentsExploration pollutes context
SkillsOn-demand knowledgeDomain expertise needed

Most agents never need to go beyond Level 2.

Show full SKILL.md (217 more words)Show less

Domain Examples

Business: CRM queries, email, calendar, approvals Research: Database search, document analysis, citations Operations: Monitoring, tickets, notifications, escalation Creative: Asset generation, editing, collaboration, review

The pattern is universal. Only the capabilities change.

Key Principles

  1. The model IS the agent - Code just runs the loop
  2. Capabilities enable - What it CAN do
  3. Knowledge informs - What it KNOWS how to do
  4. Constraints focus - Limits create clarity
  5. Trust liberates - Let the model reason
  6. Iteration reveals - Start minimal, evolve from usage

Anti-Patterns

PatternProblemSolution
Over-engineeringComplexity before needStart simple
Too many capabilitiesModel confusion3-5 to start
Rigid workflowsCan't adaptLet model decide
Front-loaded knowledgeContext bloatLoad on-demand
MicromanagementUndercuts intelligenceTrust the model

Resources

Philosophy & Theory:

  • references/agent-philosophy.md - Deep dive into why agents work

Implementation:

  • references/minimal-agent.py - Complete working agent (~80 lines)
  • references/tool-templates.py - Capability definitions
  • references/subagent-pattern.py - Context isolation

Scaffolding:

  • scripts/init_agent.py - Generate new agent projects

The Agent Mindset

From: "How do I make the system do X?" To: "How do I enable the model to do X?"

From: "What's the workflow for this task?" To: "What capabilities would help accomplish this?"

The best agent code is almost boring. Simple loops. Clear capabilities. Clean context. The magic isn't in the code.

Give the model capabilities and knowledge. Trust it to figure out the rest.

© shareAI-lab, MIT. Rendered from Markdown: HTML in the file is shown as text, images as links, and headings moved down two levels. Raw file

Files

SKILL.md and 5 other files (scripts, references) in skills/agent-builder of shareAI-lab/learn-claude-code.

  • SKILL.md
  • references/agent-philosophy.md
  • references/minimal-agent.py
  • references/subagent-pattern.py
  • references/tool-templates.py
  • scripts/init_agent.py

Open the folder on GitHubat commit ce8f9f1

Used in 7 other repositories

We found 7 copies of this SKILL.md (exact, near-identical or edited) in other folders, from 6 other GitHub owners. This page covers the copy in shareAI-lab/learn-claude-code, which our catalogue first saw on October 7, 2026.

Compare with similar skills

Agent Builder 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.

Agent Builder compared with similar skills
SkillStarsUsed inTokensAuto-checkLicenceRepo updated
Agent Builder this skillshareAI-lab/learn-claude-code78k6 repos~1.2kAutomated safety check: PassMIT
Langgraph Agent Patternssoba-labs/langchain-agent-skills107—~3.6kAutomated safety check: PassMIT
Agent CreatorOpenHands/extensions158—~1.8kAutomated safety check: PassMIT
Pydantic AI Harnesspydantic/pydantic-ai20k—~4.9kAutomated safety check: PassMIT
Agent BuildershareAI-lab/lab-skills314—~1.4kAutomated safety check: PassApache-2.0
Agent BuilderNangoHQ/nango13k2 repos~5.2kAutomated safety check: PassCustom licence

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Questions about Agent Builder

What does Agent Builder do?

Design and build AI agents for any domain. An agent skill from shareAI-lab/learn-claude-code. Agent Builder is an agent skill from shareAI-lab/learn-claude-code. Design and build AI agents for any domain.

When should I use Agent Builder?

Agent Builder fits situations like: ask to create an agent; build an assistant; design an AI system; want to understand agent architecture.

How do I install Agent Builder in Claude Code?

Run `npx skills add shareAI-lab/learn-claude-code --skill agent-builder -a claude-code`. Or copy the skill folder (skills/agent-builder in shareAI-lab/learn-claude-code) into .claude/skills/agent-builder in your project. Claude Code loads it when a task matches its description.

How do I install Agent Builder in Codex?

Run `npx skills add shareAI-lab/learn-claude-code --skill agent-builder -a codex`. Or copy the skill folder (skills/agent-builder in shareAI-lab/learn-claude-code) into .agents/skills/agent-builder in your project. Codex loads it when a task matches its description.

Can I use Agent Builder 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 shareAI-lab/learn-claude-code --skill agent-builder -a cursor` (or -a gemini-cli, github-copilot or opencode for the others). To copy it by hand, put the folder in .cursor/skills/agent-builder, .gemini/skills/agent-builder, .github/skills/agent-builder and .opencode/skills/agent-builder in your project.

What does Agent Builder need to run?

Going by SKILL.md and its folder, Agent Builder needs Python for the scripts in its folder. Our summary lists: Python 3.

Does Agent Builder 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 Agent Builder 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. The check reads SKILL.md only: the scripts in the folder are not scanned, so read them before running anything.

What licence does Agent Builder use?

Agent Builder is published under the MIT licence (the repository's licence). It allows redistribution, so the full SKILL.md is shown on this page.

How many tokens does Agent Builder use?

About 1.2k tokens (SKILL.md is roughly 4.7k characters). Agents keep only the skill's name and description in context until a task matches; then they load SKILL.md in full. Its references folder adds about 7k tokens, read only when the agent opens those files.

What are the alternatives to Agent Builder?

Skills that share tags, products or a category with Agent Builder: Langgraph Agent Patterns (soba-labs/langchain-agent-skills, 107 stars), Agent Creator (OpenHands/extensions, 158 stars), Pydantic AI Harness (pydantic/pydantic-ai, 20k stars) and Agent Builder (shareAI-lab/lab-skills, 314 stars). The comparison table on this page puts their stars, adoption, token cost, safety result and licence side by side.

Who maintains Agent Builder?

shareAI-lab (a GitHub organization) maintains it in shareAI-lab/learn-claude-code, which has 78,138 GitHub stars. The repository holds 4 skills in this directory. The repository was last updated on September 28, 2026.

Source: shareAI-lab/learn-claude-code on GitHub. Facts on this page come from the repository at the commit we read; the author's words are quoted as theirs.