Agent Builder
shareAI-lab/learn-claude-code
Design and build AI agents for any domain. An agent skill from shareAI-lab/learn-claude-code.
Create, edit, or inspect Berd agents/personas stored as Agent Markdown files with YAML frontmatter under ~/.agents/agents.
Install Agent Builder
$ npx skills add block/berd --skill agent-builder -a claude-codeProject install by default; add -g for ~/.claude/skills/.
$ gh skill install block/berd agent-builder --agent claude-codeProject scope by default; add --scope user for a personal install. Needs GitHub CLI 2.90.0 or later (public preview).
$ git clone --depth 1 https://github.com/block/berd.git skills-src && mkdir -p .claude/skills && cp -r skills-src/distro/skills/agent-builder .claude/skills/agent-builder && rm -rf skills-srcUse ~/.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/
Install the "agent-builder" agent skill from https://github.com/block/berd/tree/main/distro/skills/agent-builder into .claude/skills/agent-builder/ in this project. Copy the whole folder (SKILL.md and every file beside it), keep the folder name "agent-builder", then confirm the skill loads.Claude Code copies the folder itself, the same result as the manual copy. Check what it changed before you commit it.
$skill-installer install https://github.com/block/berd/tree/main/distro/skills/agent-builderType this inside Codex. $skill-installer <name> installs a curated skill from openai/skills. The installer writes to $CODEX_HOME/skills (default ~/.codex/skills). Restart Codex if the skill does not show up.
$ npx skills add block/berd --skill agent-builder -a codexProject install goes to .agents/skills/; add -g for ~/.codex/skills/.
$ gh skill install block/berd agent-builder --agent codexProject scope by default (.agents/skills/); add --scope user for a personal install.
$ git clone --depth 1 https://github.com/block/berd.git skills-src && mkdir -p .agents/skills && cp -r skills-src/distro/skills/agent-builder .agents/skills/agent-builder && rm -rf skills-srcUse ~/.agents/skills/ instead of .agents/skills for a personal install.
Codex skills documentation · loads skills from .agents/skills/
Install the "agent-builder" agent skill from https://github.com/block/berd/tree/main/distro/skills/agent-builder into .agents/skills/agent-builder/ in this project. Copy the whole folder (SKILL.md and every file beside it), keep the folder name "agent-builder", then confirm the skill loads.Codex copies the folder itself, the same result as the manual copy. Check what it changed before you commit it.
$ npx skills add block/berd --skill agent-builder -a cursorProject install goes to .agents/skills/; add -g for ~/.cursor/skills/.
$ gh skill install block/berd agent-builder --agent cursorProject scope by default (.agents/skills/); add --scope user for a personal install.
$ git clone --depth 1 https://github.com/block/berd.git skills-src && mkdir -p .cursor/skills && cp -r skills-src/distro/skills/agent-builder .cursor/skills/agent-builder && rm -rf skills-srcUse ~/.cursor/skills/ instead of .cursor/skills for a personal install.
Cursor skills documentation · loads skills from .cursor/skills/, .agents/skills/, .claude/skills/, .codex/skills/
Install the "agent-builder" agent skill from https://github.com/block/berd/tree/main/distro/skills/agent-builder into .cursor/skills/agent-builder/ in this project. Copy the whole folder (SKILL.md and every file beside it), keep the folder name "agent-builder", then confirm the skill loads.Cursor copies the folder itself, the same result as the manual copy. Check what it changed before you commit it.
$ gemini skills install https://github.com/block/berd.git --path distro/skills/agent-builder--scope user (default) or --scope workspace; --path is the subfolder of the repo that holds the skill; --consent skips the security confirmation prompt.
$ npx skills add block/berd --skill agent-builder -a gemini-cliProject install goes to .agents/skills/; add -g for ~/.gemini/skills/.
$ gh skill install block/berd agent-builder --agent gemini-cliProject scope by default (.agents/skills/); add --scope user for a personal install.
$ git clone --depth 1 https://github.com/block/berd.git skills-src && mkdir -p .gemini/skills && cp -r skills-src/distro/skills/agent-builder .gemini/skills/agent-builder && rm -rf skills-srcUse ~/.gemini/skills/ instead of .gemini/skills for a personal install, then run /skills reload.
Gemini CLI skills documentation · loads skills from .gemini/skills/, .agents/skills/
Install the "agent-builder" agent skill from https://github.com/block/berd/tree/main/distro/skills/agent-builder into .gemini/skills/agent-builder/ in this project. Copy the whole folder (SKILL.md and every file beside it), keep the folder name "agent-builder", then confirm the skill loads.Gemini CLI copies the folder itself, the same result as the manual copy. Check what it changed before you commit it.
$ gh skill install block/berd agent-builderInstalls for Copilot at project scope by default; add --scope user for a personal install. Preview a skill first with gh skill preview. Needs GitHub CLI 2.90.0 or later (public preview).
$ npx skills add block/berd --skill agent-builder -a github-copilotProject install goes to .agents/skills/; add -g for ~/.copilot/skills/.
$ git clone --depth 1 https://github.com/block/berd.git skills-src && mkdir -p .github/skills && cp -r skills-src/distro/skills/agent-builder .github/skills/agent-builder && rm -rf skills-srcUse ~/.copilot/skills/ instead of .github/skills for a personal install. Commit .github/skills so cloud agent and code review can use it.
GitHub Copilot skills documentation · loads skills from .github/skills/, .claude/skills/, .agents/skills/
Install the "agent-builder" agent skill from https://github.com/block/berd/tree/main/distro/skills/agent-builder into .github/skills/agent-builder/ in this project. Copy the whole folder (SKILL.md and every file beside it), keep the folder name "agent-builder", then confirm the skill loads.GitHub Copilot copies the folder itself, the same result as the manual copy. Check what it changed before you commit it.
$ npx skills add block/berd --skill agent-builder -a opencodeOpenCode documents no install command of its own. Project install goes to .agents/skills/; add -g for ~/.config/opencode/skills/.
$ gh skill install block/berd agent-builder --agent opencodeProject scope by default (.agents/skills/); add --scope user for a personal install.
$ git clone --depth 1 https://github.com/block/berd.git skills-src && mkdir -p .opencode/skills && cp -r skills-src/distro/skills/agent-builder .opencode/skills/agent-builder && rm -rf skills-srcUse ~/.config/opencode/skills/ instead of .opencode/skills for a personal install.
OpenCode skills documentation · loads skills from .opencode/skills/, .claude/skills/, .agents/skills/
Install the "agent-builder" agent skill from https://github.com/block/berd/tree/main/distro/skills/agent-builder into .opencode/skills/agent-builder/ in this project. Copy the whole folder (SKILL.md and every file beside it), keep the folder name "agent-builder", then confirm the skill loads.OpenCode copies the folder itself, the same result as the manual copy. Check what it changed before you commit it.
Facts
- Skill name
agent-builder- GitHub stars
- 969
- Token cost
- ~644 tokens
- SKILL.md length
- 305 words
- Files
- 1
- Skills in repo
- 11
- Repo updated
- First seen
- Licence
- Apache-2.0
At a glance
Create, edit, or inspect Berd agents/personas stored as Agent Markdown files with YAML frontmatter under ~/.agents/agents.
- User needs to manage Berd agents
- SKILL.md covers Storage, Format, Names and Slugs and Workflow
- Instructions only: no scripts, shell commands, URLs or credentials in SKILL.md
- Tasks that involve Building AI agents
What it does
Agent Builder is an agent skill from block/berd, published by the product's own GitHub organization. Create, edit, or inspect Berd agents/personas stored as Agent Markdown files with YAML frontmatter under ~/.agents/agents. Use when user needs to manage Berd agents or personas.
Its SKILL.md is about 640 tokens, which your agent loads only when the skill is triggered. It is a single SKILL.md file with no bundled scripts.
It sits in AI & LLM Engineering, covering Building AI agents. The repository describes itself as: a desktop app for getting work done with any model. The licence is Apache-2.0.
When your agent uses it
- User needs to manage Berd agents
- Tasks that involve Building AI agents
Example prompts
- “/agent-builder”
What it can do on your machine
Read from SKILL.md and the folder at commit 5bcf29b. 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 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 644 tokens when it runs. Until then it costs about 48 tokens; SKILL.md has 305 words of instructions outside code blocks.
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
The full file from block/berd at commit 5bcf29b, republished under its Apache-2.0 licence (© block). 305 words, ~644 tokens.
Download SKILL.mdSave it as
.claude/skills/agent-builder/SKILL.md (or your agent's skills folder).- name
- agent-builder
- description
- Create, edit, or inspect Berd agents/personas stored as Agent Markdown files with YAML frontmatter under ~/.agents/agents. Use when user needs to manage Berd agents or personas.
- metadata.berdBundled
- true
Agent Builder
Use this skill when managing Berd agents/personas in Agent Markdown format.
Storage
Agents are UTF-8 Markdown files with YAML frontmatter:
- Global:
~/.agents/agents/<slug>.md - Project-local:
<project>/.agents/agents/<slug>.md
Default to global unless the user asks for project-local. Use platform path APIs or shell-safe home expansion.
Format
Each agent is one .md file:
---
name: Agent Name
description: A concise summary of what this agent does
provider: optional-provider
model: optional-model
avatar: optional-avatar
---
Agent instructions here.Required frontmatter keys are name and description. The description must be a trimmed, non-empty summary of what the agent does; never create or save an agent with a missing, blank, or placeholder description. If the user has not supplied enough context to write an accurate description, ask for one before saving. Preserve all other frontmatter keys when editing existing agents unless the user explicitly changes them. The Markdown body is the agent’s system prompt/persona instructions.
When writing or generating a description or body, do not assign the agent a gender or gendered pronouns unless the user asked for one. Use it/its or they/them for the agent, matching how it is framed (tool vs. character), or avoid pronouns; people the instructions describe get they/them. Preserve pronouns the user chose, in either direction.
Names and Slugs
For create/rename, require a trimmed name that is non-empty, ≤80 characters, and contains no / or \.
Derive <slug> from the name by lowercasing, replacing each non-ASCII alphanumeric run with -, collapsing/trimming -, truncating to 64 characters, and falling back to agent.
Write <slug>.md; on create collisions, use <slug>-2.md, <slug>-3.md, etc.
Workflow
When editing, read the existing file first. Resolve targets by exact path, frontmatter name, then slug filename. Ask only if multiple matches remain.
Prefer direct file edits over helper scripts. Do not require Python, Node, or another runtime unless the current repo already requires it.
After writing, verify that the file exists, frontmatter is valid, name and description are both trimmed and non-empty, and preserved metadata was not removed. Report the final path.
© block, Apache-2.0. Rendered from Markdown: HTML in the file is shown as text, images as links, and headings moved down two levels. Raw file
Files
Just SKILL.md in distro/skills/agent-builder of block/berd.
Open the folder on GitHubat commit 5bcf29b
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.
| Skill | Stars | Used in | Tokens | Auto-check | Licence | Repo updated |
|---|---|---|---|---|---|---|
| Agent Builder this skillblock/berd | 969 | — | ~644 | Automated safety check: Pass | Apache-2.0 | |
| Agent BuildershareAI-lab/learn-claude-code | 78k | 6 repos | ~1.2k | Automated safety check: Pass | MIT | |
| Azure AI Projects Python SDKmicrosoft/skills | 3.1k | 6 repos | ~2.8k | Automated safety check: Pass | MIT | |
| Paperclip Create Agentpaperclipai/paperclip | 99k | 1 repos | ~2.1k | Automated safety check: Pass | MIT | |
| Senior Prompt Engineermaslennikov-ig/claude-code-orchestrator-kit | 260 | 4 repos | ~1.4k | Automated safety check: Pass | Custom licence | |
| Create Agentgnekt/My-Brain-Is-Full-Crew | 3.9k | — | ~3.1k | Automated safety check: Pass | Custom licence |
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Related
Categories
Questions about Agent Builder
What does Agent Builder do?
Create, edit, or inspect Berd agents/personas stored as Agent Markdown files with YAML frontmatter under ~/.agents/agents. Agent Builder is an agent skill from block/berd, published by the product's own GitHub organization.agents/agents.
When should I use Agent Builder?
Agent Builder fits situations like: user needs to manage Berd agents; tasks that involve Building AI agents.
How do I install Agent Builder in Claude Code?
Run `npx skills add block/berd --skill agent-builder -a claude-code`. Or copy the skill folder (distro/skills/agent-builder in block/berd) 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 block/berd --skill agent-builder -a codex`. Or copy the skill folder (distro/skills/agent-builder in block/berd) 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 block/berd --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 is published under the Apache-2.0 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 644 tokens (SKILL.md is roughly 2.6k 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), Azure AI Projects Python SDK (microsoft/skills, 3.1k stars), Paperclip Create Agent (paperclipai/paperclip, 99k stars) and Senior Prompt Engineer (maslennikov-ig/claude-code-orchestrator-kit, 260 stars). The comparison table on this page puts their stars, adoption, token cost, safety result and licence side by side.
Who maintains Agent Builder?
block (a GitHub organization, an official publisher) maintains it in block/berd, which has 969 GitHub stars. The repository holds 11 skills in this directory. The repository was last updated on October 7, 2026.
Source: block/berd on GitHub. Facts on this page come from the repository at the commit we read; the author's words are quoted as theirs.