Reactive Extensions

Reactive MCP Server is a .NET 10 Model Context Protocol server for helping AI agents and developers design, debug, review, and modernize Reactive Extensions based applications.

It ships with an embedded offline knowledge catalog, so MCP clients can use the server without any DeepWiki or web dependency at runtime.

The server exposes guidance for:

• Rx.NET architecture and core abstractions
• push vs pull sequence design
• observable operators and scheduler selection
• subject selection and subject misuse detection
• deterministic testing with TestScheduler and virtual time
• performance and benchmark-aware review guidance
• migration from ad hoc events and legacy reactive code toward clearer pipelines
• choosing between IObservable<T>, IAsyncEnumerable<T>, Ix, and AsyncRx
• richer review heuristics for real C# snippets, including example replacement code

The server is implemented in C# on net10.0 using:

• ModelContextProtocol 1.2.0

Quick Install

Click to install in your preferred environment:

VS Code - Install Reactive MCP VS Code Insiders - Install Reactive MCP Visual Studio - Install Reactive MCP

Note:

• These install links are prepared for the intended NuGet package identity CP.ReactiveUI.Mcp.Server.
• If the latest package has not been published yet, use the manual source-build configuration below.

Offline-first behavior

All MCP guidance is served from embedded manifests and compiled code-review heuristics in this repository. No runtime internet access is required for catalog lookups, reviews, prompts, or debugging guidance.

Available MCP tools

• reactive_catalog_list
• reactive_catalog_search
• reactive_catalog_get
• reactive_recommend
• reactive_review_plan
• reactive_review_csharp
• reactive_compare
• reactive_debug_checklist
• reactive_upgrade_plan
• reactive_scaffold_prompt

Available MCP resources

• reactive://catalog
• reactive://ecosystem/{id}
• reactive://best-practices/debugging

Available MCP prompts

• create_reactive_app
• debug_reactive_pipeline
• modernize_reactive_codebase

Richer review heuristics

reactive_review_plan now produces stronger feedback for real C# snippets and plans, including:

• undisposed Subscribe(...) calls
• Subject<T> used as a mutable state store
• async void
• sleep-based timing tests
• event-handler code that should be converted with Observable.FromEventPattern
• scheduler-boundary issues involving ObserveOn, SubscribeOn, UI threads, or dispatchers

Findings can include best-practice replacement snippets so the review output is directly actionable. The dedicated reactive_review_csharp tool is intended for reviewing real C# snippets separately from broader plan review.

MCP metadata

Server metadata file:

• .mcp/server.json

Current working identifiers:

• MCP server name: io.github.chrispulman/reactive-mcp-server
• package id: CP.Reactive.Mcp.Server
• version: 0.1.0

Notes for future publishing

Before publishing the package, update:

• package metadata in src/ReactiveMcp.Server/ReactiveMcp.Server.csproj
• version in .mcp/server.json
• install badge links if the package id or version changes

License

MIT License — see LICENSE.

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CP.Reactive.Mcp.Server - Empowering Agentic Automation with Reactive Technology ⚡🏭