Reactive Playground vs MCP Replay

Reactive Playground is a visual learning app for reactive programming. Instead of reading operator definitions only, you can play with marble timelines directly. Pick a category, open an operator, move events around, edit their values, clone items, remove them, or turn them into errors and completed events. The output updates live so you can understand what each operator really does. Explore operator categories such as: Transforming Filtering Combining Error Handling Utility Each playground shows a source timeline, an output timeline, a short explanation, and a code-style example. It is useful for learning ReactiveX concepts, reviewing operators, or quickly refreshing how a stream behaves before using it in code. Reactive Playground is made for developers, students, and anyone learning Rx-style reactive programming.

MCP Replay is a trace viewer for the Model Context Protocol, the open standard AI agents use to call tools. Record a session with the free mcp-tape command line tool, then open it on your phone: every request, response, error, and latency, organized and searchable. WHAT YOU CAN DO - Open .jsonl traces from Files, AirDrop, or any share sheet - Follow a replay link someone sent you, or paste a bare share ID - Watch a live session streaming from mcp-tape on your own network - See paired tool calls with latencies, and per-tool stats (count, errors, avg, p95) - Filter the timeline by tool or method - Share a trace as a link that expires after 30 days, with a delete token so you stay in control BUILT FOR PRIVACY Traces stay on your phone. Nothing is uploaded unless you explicitly share a trace, and there are no accounts, no analytics, and no tracking. Live mode connects directly to your own computer; the stream never touches a server. FOR ANYONE BUILDING WITH AGENTS If you use Claude, ChatGPT, or any MCP-compatible agent framework and have ever asked "what did it actually do?", this is the answer. Record with one command: npx mcp-tape -- your-mcp-server-command Then open the trace here or at mcpreplay.dev. MCP Replay is open source and independent. It works with any tool that emits the open mcp-tape trace format.