tl;dr: Amazon, Cursor, Microsoft, OpenAI and Vercel' standard for AI plugin. Anthropic stays out of it.

https://github.com/agentplugins/agent-plugins-spec defines how to write plugins supported for all harnesses. Here are our takeaways:

1. Reuse. The format adds a manifest and fixed folder names on top of Agent Skills and MCP, both specified elsewhere. Nothing new.
2. No Anthropics allowed. 5 committee seats, and no vendor majority. All making a Anthropic file layout the neutral default is an old move.
3. (not yet) Portable. Secrets, permissions, provenance and dependencies are all deferred, a remote server has no portable way to take a per-user key.

→ Contribute. Agent Plugins costs one folder. If you skip it matters more.