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Agent skill

Agent Builder

by NangoHQ in NangoHQ/nango

A skill your agent uses when creating, improving, or troubleshooting Claude Code subagents.

Custom licenceAuto-check passedAI & LLM Engineering

Install Agent Builder

skills CLI
$ npx skills add NangoHQ/nango --skill agent-builder -a claude-code

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

GitHub CLI
$ gh skill install NangoHQ/nango 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/NangoHQ/nango.git skills-src && mkdir -p .claude/skills && cp -r skills-src/.agents/skills/agent-builder-skill .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
13k
Used in
2 other repos
Token cost
~5.2k tokens
SKILL.md length
1,177 words
Files
2
Skills in repo
9
Repo updated
First seen
Licence
Custom licence

At a glance

A skill your agent uses when creating, improving, or troubleshooting Claude Code subagents.

  • Works in 12 steps: Identify the Use Case → Design Agent Scope → Write the System Prompt → …
  • Troubleshooting Claude Code subagents
  • SKILL.md covers When to Use This Skill, Quick Reference, Creating Effective Subagents and Agent Patterns, plus 3 more sections
  • Instructions only: no scripts, shell commands, URLs or credentials in SKILL.md

What it does

Agent Builder is an agent skill from NangoHQ/nango. Use when creating, improving, or troubleshooting Claude Code subagents. Expert guidance on agent design, system prompts, tool access, model selection, and best practices for building specialized AI assistants.

Its SKILL.md is about 5.2k tokens, which your agent loads only when the skill is triggered. The skill folder holds 1 other file (for example `EXAMPLES.md`).

It sits in AI & LLM Engineering, covering Building AI agents, Subagents and Design systems. The repository describes itself as: Connect your agents & product to 1,000 APIs.

When your agent uses it

  • Troubleshooting Claude Code subagents
  • Tasks that involve Building AI agents
  • Tasks that involve Subagents

Example prompts

  • “/agent-builder”

Workflow steps

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

  1. Identify the Use Case
  2. Design Agent Scope
  3. Write the System Prompt
  4. Configure Tools Access
  5. Choose Model
  6. Write Clear Description
  7. Single Responsibility
  8. Detailed System Prompts
  9. Minimum Tool Access
  10. Clear Output Formats
  11. Version Control
  12. Iterative Improvement

What it can do on your machine

Read from SKILL.md and the folder at commit 1ed967d. 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 yaml and markdown).

    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 5.2k tokens when it runs. Until then it costs about 56 tokens; SKILL.md has 1,177 words of instructions outside code blocks.

Always · name and description, kept in context so the agent knows when to use it
~56
When it runs · the whole SKILL.md, loaded when a task matches
~5.2k

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); files beside SKILL.md are not scanned.

SKILL.md

Its licence (Custom licence) doesn't allow us to republish the file, so here is its outline and opening line. It has 1,177 words (~5,188 tokens).

“Use this skill when creating, improving, or troubleshooting Claude Code subagents. Provides expert guidance on agent design, system prompt engineering, tool configuration, and delegation patterns.”

— opening of SKILL.md by NangoHQ, Custom licence
name
agent-builder
tags
meta
globs
**/.claude/agents/**/*.md, **/.claude/agents/**/*.markdown
alwaysApply
false

Read the full SKILL.md on GitHub

Files

SKILL.md and 1 other file in .agents/skills/agent-builder-skill of NangoHQ/nango.

  • SKILL.md
  • EXAMPLES.md

Open the folder on GitHubat commit 1ed967d

Used in 2 other repositories

We found 5 copies of this SKILL.md (exact, near-identical or edited) in other folders, from 2 other GitHub owners. This page covers the copy in NangoHQ/nango, 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 skillNangoHQ/nango13k2 repos~5.2kAutomated safety check: PassCustom licence
Agent BuildershareAI-lab/learn-claude-code78k6 repos~1.2kAutomated safety check: PassMIT
Terminal Outputswamp-club/swamp642—~2.1kAutomated safety check: PassCustom licence
Langgraph Agent Patternssoba-labs/langchain-agent-skills107—~3.6kAutomated safety check: PassMIT
Richard S SuttonK-Dense-AI/mimeo282—~1.8kAutomated safety check: PassMIT
Agent CreatorOpenHands/extensions157—~1.8kAutomated safety check: PassMIT

Similar skills

  • Agent Builder

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    AI & LLM EngineeringAuto-check passed

  • Terminal Output

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    282 GitHub stars~1.8k tokensUpdated 1 mo ago
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    157 GitHub stars~1.8k tokensUpdated today
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Categories

Questions about Agent Builder

What does Agent Builder do?

A skill your agent uses when creating, improving, or troubleshooting Claude Code subagents. Agent Builder is an agent skill from NangoHQ/nango. Use when creating, improving, or troubleshooting Claude Code subagents.

When should I use Agent Builder?

Agent Builder fits situations like: troubleshooting Claude Code subagents; tasks that involve Building AI agents; tasks that involve Subagents.

How do I install Agent Builder in Claude Code?

Run `npx skills add NangoHQ/nango --skill agent-builder -a claude-code`. Or copy the skill folder (.agents/skills/agent-builder-skill in NangoHQ/nango) 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 NangoHQ/nango --skill agent-builder -a codex`. Or copy the skill folder (.agents/skills/agent-builder-skill in NangoHQ/nango) 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 NangoHQ/nango --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?

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

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. Review the folder before installing.

What licence does Agent Builder use?

Agent Builder has a licence file (the repository's licence) that doesn't match a standard licence. Read it on GitHub before reusing the skill.

How many tokens does Agent Builder use?

About 5.2k tokens (SKILL.md is roughly 21k 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 Agent Builder?

Skills that share tags, products or a category with Agent Builder: Agent Builder (shareAI-lab/learn-claude-code, 78k stars), Terminal Output (swamp-club/swamp, 642 stars), Langgraph Agent Patterns (soba-labs/langchain-agent-skills, 107 stars) and Richard S Sutton (K-Dense-AI/mimeo, 282 stars). The comparison table on this page puts their stars, adoption, token cost, safety result and licence side by side.

Who maintains Agent Builder?

NangoHQ (a GitHub organization) maintains it in NangoHQ/nango, which has 12,545 GitHub stars. The repository holds 9 skills in this directory. The repository was last updated on October 7, 2026.

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