What is agent-plugin-sdk?

agent-plugin-sdk is a TypeScript toolkit for developers who build plugins for AI coding assistants. The problem it solves: assistants like Claude Code, Codex, Gemini CLI, Copilot, Cursor, Windsurf, Pi, and OpenCode each expect plugins in their own file layout and format. Instead of writing a separate plugin for every one of those tools, you define your plugin once in TypeScript, and the SDK compiles it into the exact native files each assistant already knows how to load. There is no extra runtime sitting between your plugin and the assistant, the output is just the plain files that assistant would normally read. A plugin definition can include several kinds of pieces: always-on instructions that guide the assistant, reusable skills with their own descriptions and steps, slash commands, subagents with their own prompts and tools, lifecycle hooks, MCP server configuration, shared tool implementations written in TypeScript, and companion files to copy alongside everything else. Not every assistant supports every one of these pieces, so the project keeps a support matrix documenting what each assistant can use. Two commands do the main work. Running ap-sdk build turns your definition into a folder of output subfolders, one for each supported assistant. Running ap-sdk install copies those generated files into the right local folders for whichever assistants you have installed. If you already have a plugin written directly for one of these tools, such as Claude Code or Cursor, a command called ap-sdk port can read that existing plugin and generate a portable TypeScript definition from it instead of asking you to start over. You can also install a plugin straight from a GitHub repository using ap-sdk install owner/repo. The project installs as an npm package with pnpm add -D @jalco/ap-sdk, and it is a fairly young project with 12 stars so far. It carries an MIT license and credits Sahaj Jain as the original creator, continued now by Justin Levine.