Authoring Guide

Add a plugin

Create plugins/<id>/ with a focused purpose.
Add only applicable surfaces: agents/, commands/, skills/, mcps/, and README.md.
Add .claude-plugin/plugin.json and .codex-plugin/plugin.json when those hosts are supported.
Register the plugin in both root marketplace files.
Add tests or Vally evaluations under tests/<id>/.
Update plugins.md, README links, and the solution when a .NET project is added.

Add a skill

Create plugins/<id>/skills/<name>/SKILL.md with valid frontmatter. Keep activation guidance precise and place supporting material beside the skill instead of inflating its core instructions.

Add an MCP

Keep implementation inside plugins/<id>/mcps/. Bound public URL, redirects, response size, timeouts, origins, and credentials. Put endpoint metadata in the plugin package, never secrets.

Add tests

Use tests/<id>/unit-tests/ for fast isolated tests and tests/<id>/integration-tests/ for hosting, networking, or external boundaries. .NET tests target net10.0, use xUnit v3 with xunit.v3.core.mtp-v2, Shouldly, and Microsoft Testing Platform.

Review checklist

Plugin purpose and ownership are clear.
Host manifests contain matching name and version.
No credentials or generated bin/ and obj/ files are committed.
Tests or evaluations cover new behavior.
Focused validation and relevant broader validation pass.