chapplin

chapplin is a ChatGPT Apps framework. This allow developers to create MCP servers for OpenAI Apps SDK with type-safe JSX.

• Type-safe tools
• JSX-based app rendering
• Framework agnostic
  • Hono, Express, Fastify, etc. for server
  • React, Preact, Hono for UI

Usage

npm create chapplin@latest

Example Todo tool

import { defineTool } from "chapplin/tool";
import z from "zod";
export default defineTool(
	"get",
	{
		inputSchema: {},
		outputSchema: {
			todos: z.array(z.object({ id: z.number(), title: z.string(), completed: z.boolean() })),
		},
	},
	async () => {
		const todos = await fetchTodos();
		return {
			content: [{ type: "text", text: `${todos.length} todos remaining.` }],
			structuredContent: { todos },
		};
	},
	{
		app: ({ toolOutput }) => (
			<div>
				<h1>GET Tool Example</h1>
				<p>Status: {toolOutput?.todos.length} todos remaining.</p>
				<ul>
					{toolOutput?.todos.map((todo) => (
						<li key={todo.id}>
							{todo.title} - {todo.completed ? "Completed" : "Pending"}
						</li>
					))}
				</ul>
			</div>
		),
	},
);

License

MIT