Build AI agent skills, block by block.Skill Builder is a free web app for designing AI agent skills (SKILL.md) and agent definitions with drag-and-drop blocks, then exporting them as markdown for Claude Code, GitHub Copilot and OpenAI Codex. It needs JavaScript to run. Your work is saved in your browser and works offline. Nothing leaves your device unless you turn on an optional feature such as GitHub sync.Open Skill Builder · See how it works

Free

No sign-up

Works offline

Your work stays in your browser

Exports for Claude Code, GitHub Copilot, OpenAI Codex, Cursor.From idea to every AI tool, in three steps

Drag in blocks. Start from a template or a built-in skill. Each section of a skill is a block: purpose, steps, examples, limits.

Check and save. Live checks follow the Agent Skills specification. Save a version whenever you are happy, and compare or restore any of them.

Export for every tool. Download a zip of plain markdown, with folders and notes for each AI tool. No lock-in: the files are yours.

Never written a skill? Start here.A skill is a short markdown playbook that teaches an AI tool one job. You do not need to know the format: the blocks and the checks do.

Start from a ready-made template.

A guided walkthrough shows each step.

Plain-language checks say what to fix, and why.

Take the walkthrough · Browse the blocksSkills your whole team can trust.Treat skills like code: versioned, checked and portable, so every AI tool behaves the same way.

Saved versions you can compare and restore.

Specification checks and a security scan.

Optional GitHub sync, in beta.

Explore the Library · Check a SKILL.mdLet your AI tool build with you.Connect your AI tool and work on the same project, with every change asked about and undoable.

Connect AI works over MCP, and is off until you turn it on.

Loops that repeat until a check passes.

Promptor builds and reviews your prompts.

Open Promptor · Read the guideEverything a skill needs, nothing it does not

Drag-and-drop blocks. Build a skill from blocks and watch the markdown appear beside them.

A library to start from. Built-in skills and agents, and your own imports from GitHub.

Checked and safe. Specification checks as you type, and a security scan on everything you import.

Versions you can trust. Save a version, compare any two, and restore one whenever you need it.

Connect your AI tool. Claude Code, Copilot, Codex and others can work in your project, with your approval.

Sync with GitHub. Optional and in beta: keep a project in a repository, with each version a tagged commit.

Make your first skill in a few minutes.It is free, it needs no account, and your files are plain markdown you can take anywhere.