Create Plugin

Create Plugin

Create a new plugin for this repository following established conventions.

Workflow

1. Determine Plugin Type

Infer the plugin type from the user's request:

• Skills plugin: Provides instructions and workflows that Claude Code follows (e.g., style guides, multi-step procedures). Most plugins are this type.
• Command plugin: Provides slash commands that users invoke explicitly (e.g., /example-command). Commands are structured Markdown files with frontmatter, a workflow, and optional reference templates.
• Hooks plugin: Provides event-driven shell commands that run automatically in response to Claude Code lifecycle events (e.g., notifications on task completion).
• Combinations: A plugin can provide any combination of skills, commands, and hooks.

Inference heuristic: "create a command", "add a slash command", "add a /something command" implies a command plugin. "create a skill", "add a style guide", "add a workflow" implies a skills plugin. "create a hook", "add a notification" implies a hooks plugin.

If the request doesn't imply a type (e.g., just "create a plugin"), ask. If ambiguous, default to a skills plugin.

2. Choose a Name

The plugin name must be:

• Kebab-case (e.g., write-go-code, suggest-next-issue)
• Verb-noun preferred (e.g., create-worktree-from-issue, resolve-copilot-pr-feedback)
• Descriptive of what the plugin does
• Unique within the plugins/ directory

If the user provided a name, use it. Otherwise, generate a descriptive name from the plugin's purpose and proceed.

3. Create Directory Structure

No manual mkdir is needed — the Write tool creates parent directories automatically when writing files. The directories below are created implicitly when their first file is written in the subsequent steps.

Skills Plugin

plugins/PLUGIN-NAME/.claude-plugin/
plugins/PLUGIN-NAME/skills/PLUGIN-NAME/

Add a references/ subdirectory if the skill needs supplementary documentation:

plugins/PLUGIN-NAME/skills/PLUGIN-NAME/references/

Command Plugin

plugins/PLUGIN-NAME/.claude-plugin/
plugins/PLUGIN-NAME/commands/

Add a references/ directory if the command has large templates to extract:

plugins/PLUGIN-NAME/references/

Hooks Plugin

plugins/PLUGIN-NAME/.claude-plugin/
plugins/PLUGIN-NAME/hooks/
plugins/PLUGIN-NAME/scripts/

Combinations

Combine structures under the same plugin directory as needed. A plugin can have any combination of skills/, commands/, hooks/, scripts/, and references/.

4. Write plugin.json

Create .claude-plugin/plugin.json with alphabetized fields. See ./references/plugin-json.md for the full field list, versioning rules, and templates for each plugin type (Skills, Commands, Hooks).

Key points:

• New plugins start at version 1.0.0
• Include "skills": "./skills" only if the plugin provides skills
• Include "commands": "./commands" only if the plugin provides commands
• The name field must match the directory name

5. Write SKILL.md, hooks.json, or Command .md

For Skills

Create skills/PLUGIN-NAME/SKILL.md. See ./references/skill-md.md for the frontmatter format, description formula, common sections, and examples.

Key points:

• Frontmatter has exactly two fields: name and description
• The description includes trigger phrases for automatic activation
• Use >- (folded block scalar) for multi-line descriptions
• Structure the body with a ## Workflow section using numbered steps

For Commands

Create commands/COMMAND-NAME.md. See ./references/command-md.md for the frontmatter fields, argument handling, external file references, and body structure.

Key points:

• Frontmatter includes description and disable-model-invocation: true
• Add argument-hint if the command accepts arguments
• Use $ARGUMENTS and $1/$2 for argument access in the body
• Structure the body with ## Workflow numbered steps, ## Error Handling, and ## Reference: sections
• For large commands, extract templates into references/ files using @${CLAUDE_PLUGIN_ROOT}/references/file.md

For Hooks

Create hooks/hooks.json. See ./references/hooks-json.md for the JSON schema, hook categories, matchers, and examples.

Key points:

• Use ${CLAUDE_PLUGIN_ROOT} to reference scripts
• Each hook entry has "type": "command"

6. Add Scripts (if needed)

If the plugin needs executable scripts, create them under scripts/. See ./references/scripts.md for the required structure, conventions, and patterns.

Key points:

• No file extension for executables
• Must be chmod +x
• Follow the Bash conventions (shebang, strict mode, main function pattern)
• Prefix implementation functions with do_

7. Add Reference Files (if needed)

Skills and commands that need supplementary documentation or templates should place them under references/:

• Workflow skills: Use a flat references/ directory with topic-named files by default (e.g., ./references/checklist.md, ./references/github.md). If a workflow skill has enough reference files that a flat list becomes hard to scan, use topical subdirectories named for the organizing axis, such as ./references/languages/, ./references/tools/, or ./references/scripts/. Do not use ./references/essential/ plus ./references/comprehensive/ for workflow skills.
• Style-guide skills: Style-guide skills, primarily write-*, may use one canonical topic document such as ./references/BASH.md or ./references/MARKDOWN.md, or split reference material into ./references/essential/ plus ./references/comprehensive/. The split is about reading mode: condensed actionable rules versus deep topic-by-topic guidance. It is not a file-count convention.

For skills: Reference files are plain Markdown. Point to them from SKILL.md with relative paths (e.g., ./references/checklist.md).

For commands: Reference files contain templates that the command uses at runtime. Include them in the command file using the @${CLAUDE_PLUGIN_ROOT}/references/file.md pattern. Place references/ alongside commands/ (not inside it). See ./references/command-md.md for the extraction guidelines and file format.

8. Register in marketplace.json

Add a new entry to the plugins array in .claude-plugin/marketplace.json. See ./references/marketplace-json.md for the entry format, valid categories, and insertion conventions.

Key points:

• Insert alphabetically by plugin name
• Include category and source fields (not present in plugin.json)
• All shared fields must match plugin.json exactly
• Do not hand-edit .agents/plugins/marketplace.json, dist/codex/, or dist/opencode/; regenerate them with the build scripts

9. Update README.md

Add the new plugin to the current compact category-table format in root README.md, and create the required per-plugin README. See ./references/readme-updates.md for the exact format.

1. Root README category table: Add a row to the appropriate category table. For skills and command-style plugins, use the Plugin, Trigger, and What it does columns. For hooks, use the hooks table with Plugin and What it does.
2. Canonical description: Use the marketplace description field verbatim for the What it does column.
3. External tools: If the plugin requires external tools, add or update the category's **External tools:** bullet list.
4. Per-plugin README: Create plugins/PLUGIN-NAME/README.md with user-facing install, usage, requirements, examples, and related-plugin details.

Do not add a root README table of contents, H3 plugin-description section, or individual install command. The root README now uses category tables, and the marketplace flow handles installation.

10. Regenerate Generated Mirrors

Regenerate generated surfaces from the canonical plugin source and commit the generated outputs:

1. Run bin/build-codex-marketplace to update .agents/plugins/marketplace.json and dist/codex/.
2. Run bin/build-opencode-mirror to update dist/opencode/.

Do not edit generated mirror files directly. Only update project-level instruction files such as AGENTS.md or CLAUDE.md when the new plugin changes repository conventions or those files already contain a current plugin catalog that must be kept in sync.

11. Verification Checklist

Before finishing, verify:

• [ ] All new files exist with correct structure
• [ ] plugin.json fields are alphabetized and name matches the directory name
• [ ] marketplace.json is valid JSON with the new entry
• [ ] marketplace.json entry fields match plugin.json (shared fields)
• [ ] bin/build-codex-marketplace has regenerated .agents/plugins/marketplace.json and dist/codex/
• [ ] bin/build-opencode-mirror has regenerated dist/opencode/
• [ ] Root README.md has the new plugin row in the correct category table, with the marketplace description copied verbatim
• [ ] Root README.md external-tool bullets are updated if the plugin needs external tools
• [ ] plugins/PLUGIN-NAME/README.md exists and documents installation, usage, requirements, examples, and related plugins
• [ ] Project-level instruction files such as AGENTS.md or CLAUDE.md were updated only if the new plugin changes current repository conventions
• [ ] SKILL.md frontmatter has only name and description fields (skills only)
• [ ] All reference files are reachable from SKILL.md via relative paths (skills only)
• [ ] Command .md has description and disable-model-invocation: true in frontmatter (commands only)
• [ ] Command filename matches the intended slash command name (commands only)
• [ ] plugin.json includes "commands": "./commands" (commands only)
• [ ] External file references use @${CLAUDE_PLUGIN_ROOT}/references/ pattern (commands with extracted templates only)
• [ ] $ARGUMENTS handling is documented in the workflow if argument-hint is set (commands only)
• [ ] Scripts (if any) are executable
• [ ] Hooks (if any) reference scripts via ${CLAUDE_PLUGIN_ROOT}

Error Handling

• If the plugin name already exists under plugins/, ask the user for a different name
• If marketplace.json cannot be parsed as valid JSON, fix the syntax before proceeding
• If the user is unsure about the plugin type, default to a skills plugin (the most common type)
• If the user wants to add a skill to an existing plugin instead of creating a new one, bump the minor version in both plugin.json and marketplace.json
• If generated Codex or OpenCode files drift, run bin/build-codex-marketplace and bin/build-opencode-mirror instead of editing generated files directly

Source & license

This open-source skill is cataloged on AgentStack and links to its original source — we do not rehost the code.

• Author: cboone
• Source: cboone/agent-harness-plugins
• License: MIT
• Homepage: https://github.com/cboone/agent-harness-plugins

Install and usage instructions live in the source repository linked above.