codewhale-hq / plugin-creator

Plugin Creator

Use this skill when a user wants a local Codewhale plugin bundle. Trusted and
enabled bundles may add declarative Skills, commands, agents, hooks, and MCP
servers (stdio and remote) through the existing engines. LSP, filesystem
roots, and lifecycle mutation are inventory-only. Native extensions (host
code) are inventory-only unless the user has turned on the experimental
[features] extension_host flag.

Workflow

1. Pick a Codewhale-owned location:

   • User bundle: ~/.codewhale/plugins/<plugin-name>/
   • Workspace bundle: <workspace>/.codewhale/plugins/<plugin-name>/
2. Normalize the bundle name to lowercase hyphen-case.

3. Create plugin.json (Agent Plugins v1.0.0; a legacy plugin.toml stays
   readable, but new bundles use plugin.json):

{
  "$schema": "https://agent-plugins.org/schemas/plugin.json",
  "name": "my-plugin",
  "version": "0.1.0",
  "description": "What this bundle provides"
}

1. Put each Skill under skills/<skill-name>/SKILL.md; Codewhale finds
   skills/ automatically and exposes each as my-plugin:<skill-name>,
   never as an unqualified command.

2. Add MCP servers in a sibling mcp.json only when the bundle needs an
   existing MCP engine. Keep stdio commands and paths inside the bundle. Map local
   environment values only as exact ${SOURCE_ENV} references. For remote MCP,
   use HTTPS (or loopback HTTP), forbid URL user information/query/fragment,
   use only environment-backed headers or bearer tokens, and declare the exact
   normalized endpoint host set in capabilities.network_hosts under
   extensions["net.codewhale"]. Never place credentials in the manifest.

3. Commands (commands/*.md), agents (agents/*.toml), and hooks
   (hooks/*.toml), declared under extensions["net.codewhale"], activate
   under the current policy — workspace bundles win same-name collisions over
   user and built-in bundles. LSP, filesystem roots, and lifecycle mutation
   are inventory-only: declare them only when inventorying future work. A
   native entry runs only under the experimental extension host; there it
   must be one .mjs, .js or .mts ES module file, /plugin validate rejects
   anything else, and its tools always use Required approval, never a
   plugin's read-only hint. Full Access, Bypass, or an exact session grant
   for the reviewed build can satisfy that gate without a prompt. A bundle
   that declares only unsupported surfaces cannot be enabled.

4. Validate and review without executing bundle content:

   • /plugin validate <plugin-name>
   • /plugin show <plugin-name>

   • stop and present these results; the person runs /plugin enable <plugin-name>
     to open the content/capability review, reviews it, runs the exact
     /plugin trust ... confirmation shown, then enables the bundle

5. Verify /skills inspect reports plugin provenance and /plugin list
   reports the expected trust and activation state. Trust stages the reviewed
   content but does not activate it. After enablement, follow the host's
   reload notice: use /reload or a new session to apply changes to a live
   session's pinned skills and tools.

Every user and workspace bundle starts untrusted and disabled. Reuse the
existing /plugin marketplace, install, update, review and reload surfaces;
do not add a parallel installer, registry or automatic trust flow. Catalog
membership alone never installs, trusts or enables a plugin.

Experimental host code

Only scaffold host code when the person explicitly uses the experimental
extension-host feature. Start from the tested hello-extension example and
docs/EXTENSIONS.md in the Codewhale repository. A typed .mts entry may use
Node's erasable TypeScript syntax; bundle dependencies locally. Register tools
with a plugin-specific prefix and an object input schema, propagate
exec.signal, and use ctx.effect for bounded asynchronous cleanup. The
current execution context exposes signal, callId and args; it does not
expose the calling workspace path. Do not change the shared process cwd.

Stop after install, validate and show; never automate the trust token. A
person reviews, trusts and enables the bundle. /plugin show <name> reports
owner state, live tools and recent attributed diagnostics. Recovery may create
fresh registrations, but never replays an interrupted tool call. Explain the
shared-process and current platform sandbox limits without claiming isolation.