Creating Bundles

Package skills, prompts, and configs into a versioned bundle that anyone can install with a single command.

Prerequisites

musher CLI installed
A Musher account and API key (see Getting Started)
At least one text file to package (a skill, prompt, config, or rule)

Authenticate

Log in

Run musher login and enter your API key when prompted:

bash

musher login

Verify your identity

Confirm your credentials and see which namespaces you can publish to:

bash

musher whoami

Output

User:       [email protected]
Namespaces: acme (owner), acme-labs (member)

Initialize Your Bundle

Create a project directory

bash

mkdir code-review-kit && cd code-review-kit

Scaffold the bundle definition

Run musher init to generate a musher.yaml with default fields:

bash

musher init

Review the generated file

Open musher.yaml and fill in your bundle details:

musher.yaml

kind: bundle
namespace: acme
slug: code-review-kit
version: 1.0.0
name: Code Review Kit
description: Skills, prompts, and rules for consistent code reviews.
keywords:
  - code-review
  - skills
assets: []

Understanding musher.yaml

The musher.yaml file defines your bundle's identity and its assets. Here's what each field does:

Top-Level Fields

Field	Required	Description
`kind`	Yes	Always `bundle`
`namespace`	Yes	Your organization's namespace (must match a writable namespace from `musher whoami`)
`slug`	Yes	URL-safe identifier for the bundle (lowercase, hyphens)
`version`	Yes	Version string for this release
`name`	Yes	Human-readable display name
`description`	No	Short description of what the bundle provides
`keywords`	No	List of tags for discovery
`assets`	Yes	Array of asset definitions (see below)

Asset Fields

Field	Required	Description
`id`	Yes	Unique identifier for the asset within this bundle
`src`	Yes	Path to the source file, relative to `musher.yaml`
`kind`	Yes	Asset type (e.g., `skill`, `prompt`, `rule`, `config`)
`installs`	No	Array of install mappings that control where runners place the file

Install Mapping Fields

Field	Required	Description
`harness`	Yes	Target runner (e.g., `claude-code`)
`path`	Yes	Destination path within the runner's workspace

Add Your Assets

Build out your bundle by creating asset files and referencing them in musher.yaml. This example creates a code review kit with three assets.

Create a code review skill

skills/code-review/SKILL.md

---
name: Code Review
description: Perform thorough, constructive code reviews.
---

Review the provided code changes. For each file:

1. Check for bugs, security issues, and performance problems.
2. Verify error handling covers edge cases.
3. Suggest improvements to readability and maintainability.
4. Note what's done well — call out good patterns.

Be constructive. Explain *why* something should change, not just *what*.

Create a PR summary prompt

prompts/pr-summary.md

Summarize this pull request in 2-3 sentences.
Focus on what changed and why, not implementation details.
Include the risk level: low, medium, or high.

Create review rules

rules/review-standards.md

# Code Review Standards

- All public functions must have error handling.
- No hardcoded secrets or credentials.
- Test coverage required for new business logic.
- Breaking API changes require a migration guide.

Update musher.yaml with all assets

musher.yaml

kind: bundle
namespace: acme
slug: code-review-kit
version: 1.0.0
name: Code Review Kit
description: Skills, prompts, and rules for consistent code reviews.
keywords:
  - code-review
  - skills

assets:
  - id: code-review-skill
    src: skills/code-review/SKILL.md
    kind: skill
    installs:
      - harness: claude-code
        path: .claude/skills/code-review/SKILL.md

  - id: pr-summary-prompt
    src: prompts/pr-summary.md
    kind: prompt
    installs:
      - harness: claude-code
        path: .claude/rules/pr-summary.md

  - id: review-standards
    src: rules/review-standards.md
    kind: rule
    installs:
      - harness: claude-code
        path: .claude/rules/review-standards.md

The installs mappings tell the consumer's runner where to place each file. In this example, the skill goes into .claude/skills/ while the prompt and rule go into .claude/rules/ — matching Claude Code's expected file structure.

Validate

Run validation

Check that your bundle definition and asset files are valid:

bash

musher validate

Output

✓ musher.yaml is valid
✓ 3 assets found
✓ All source files exist
✓ Bundle is ready to publish

Fix any errors

If validation fails, check for these common issues:

Error	Fix
Source file not found	Check that the `src` path matches your file location
Invalid asset kind	Use a recognized kind like `skill`, `prompt`, `rule`, or `config`
Missing required field	Ensure `kind`, `namespace`, `slug`, `version`, and `name` are set
Duplicate asset ID	Each asset `id` must be unique within the bundle

Project Structure

Your completed bundle should look like this:

Directory layout

code-review-kit/
├── musher.yaml
├── skills/
│   └── code-review/
│       └── SKILL.md
├── prompts/
│   └── pr-summary.md
└── rules/
    └── review-standards.md

Common Patterns

A minimal bundle with just one skill:

musher.yaml

kind: bundle
namespace: acme
slug: sql-reviewer
version: 1.0.0
name: SQL Reviewer
description: Review SQL queries for performance and safety.

assets:
  - id: sql-review-skill
    src: SKILL.md
    kind: skill
    installs:
      - harness: claude-code
        path: .claude/skills/sql-review/SKILL.md

Next Steps

Publishing Bundles

Publish your bundle to the registry

Asset Types

All supported asset kinds and their conventions

Musher Commands

Complete CLI command reference