Beyond REST: A Pragmatic Guide to HTTP Streaming with MCP in .NET

mcp100

— 6 min read

Summary

This tutorial addresses the limitations of traditional REST APIs for long-running backend tasks, such as sluggish user experiences and inefficient polling. It introduces a modern alternative: combining the Model Context Protocol (MCP) with HTTP Streaming in .NET. MCP provides a standardized way for services to self-describe their capabilities, allowing clients to dynamically discover and use tools without being tightly coupled. HTTP Streaming enables servers to send data in real-time as it becomes available, creating a fluid, conversational user experience. Through a practical example, the guide demonstrates how to run a .NET server and use an inspector tool to discover and execute a function, highlighting the architectural benefits of this decoupled, scalable, and efficient pattern.

Table of Contents

We’ve all been there. You're building a sleek, modern UI that interacts with a powerful backend service—maybe an AI agent, a data processing pipeline, or any long-running task. You kick off a job from the frontend, and what does the user see? A spinner. A loading bar. The digital equivalent of a "please hold" message.

Behind the scenes, you're probably wrestling with a familiar dilemma. Do you use a standard REST endpoint and force the user to wait, sometimes for an uncomfortably long time, for one giant JSON response? Or do you implement a polling mechanism, where the frontend frantically asks the server every few seconds, "Are we there yet? Are we there yet? Are we there yet?" The first approach creates a sluggish user experience; the second is inefficient and feels like a workaround, not an architecture.
Beyond_REST_A_Pragmatic_Guide_to_HTTP_Streaming_with_MCP_in_NET_request_response_patterns.png
What if we could have a live, open line of communication with our backend? What if the server could send us updates, results, and data as they become available? This isn't a futuristic dream; it's what you get when you combine the Model Context Protocol (MCP) with HTTP Streaming. It's time to hang up on polling and have a real conversation with your services.

Core Concepts: A Universal Remote on a Live Wire

Let's break down the two key ideas here. They're simpler than they sound and incredibly powerful when used together.

1. Model Context Protocol (MCP): The Universal Remote

What it is: MCP is a simple, standardized protocol for interacting with services. Think of it not as a replacement for REST or gRPC, but as a universal language for describing and calling capabilities. Instead of defining custom endpoints like POST /api/v1/tools/add or GET /api/v2/resources/user-greeting, you use a standard set of methods like tools/call and resources/get.

Why it's important: Standardization is a superpower. Imagine having a universal remote that could automatically discover and control any device in your house. That's MCP for your backend. A client application can ask an MCP-enabled server, "What tools do you have?" (tools/list), and the server responds with a machine-readable "menu" of its capabilities, including what inputs each tool needs. This decouples your client from your server, allowing you to add or change backend tools without breaking your frontend.
Beyond_the_Chatbot_Giving_Your_AI_Real-World_Eyes_with_a_Web_Search_MCP_Server_mcp_architecture.png

2. HTTP Streaming: The Conveyor Belt

What it is: A traditional HTTP request-response cycle is like ordering a full meal kit. You place your order, and you get nothing until the entire box—appetizer, main course, and dessert—is packed and shipped. HTTP Streaming, on the other hand, is like a conveyor belt at a sushi restaurant. As soon as a chef prepares a plate, it's put on the belt and sent directly to you. You get to enjoy the food piece by piece, as it's made.

Why it's important: For any task that isn't instantaneous, streaming is a game-changer. An AI generating a long text response can stream it word by word. A service processing a large file can send status updates in real-time. This creates a fluid, responsive user experience and gives you a live window into the backend's process, all over a single, efficient HTTP connection.
图示：http_streaming_conveyor_belt

When you combine MCP's standardized "universal remote" with the "conveyor belt" of HTTP Streaming, you get a robust, real-time, and discoverable architecture for building modern applications.

Code in Practice: Let's See it in Action

Talk is cheap. Let's run a simple .NET service that speaks MCP over HTTP Streaming and see what this all looks like in practice.
图示：demo_architecture

Step 1: Fire Up the Server

First, we'll get our MCP-enabled .NET server running. This server exposes a simple AddNumbers tool.

Clone the repository (if you haven't already), open your terminal, and run these commands:

# Install the necessary .NET dependencies
dotnet restore

# Run the server
dotnet run

You should see output indicating that a web server is running, likely on http://localhost:3001. Leave this terminal running. Our server is now live and listening for MCP requests.

Step 2: Test with the MCP Inspector

Now, how do we talk to this server? We'll use the @modelcontextprotocol/inspector, a handy tool for testing MCP endpoints. It's our "universal remote" for this exercise.

Open a new terminal window (leave the server running in the first one) and run the following command:

npx @modelcontextprotocol/inspector http://localhost:3001

This command downloads and runs the inspector, opening a web interface in your browser. This UI is a client that will communicate with our server.
图示：inspector_ui_screenshot

Make sure the settings at the top are correct:

  • Transport Type: Streamable HTTP
  • URL: http://localhost:3001/mcp

Once connected, you can explore the server's capabilities:

  1. Click on the Tools tab. The inspector has already called tools/list behind the scenes and discovered our AddNumbers tool, along with its description and required inputs (a and b). Notice you didn't have to read any API docs—the service described itself.
  2. Click Run next to the AddNumbers tool.
  3. Enter 2 for a and 4 for b, then click Run.
  4. You'll instantly see the result: 6.

This simple interaction demonstrates the core value: a client application that can discover and execute backend functionality in a standardized way.

Step 3: The CLI for Power Users

The web UI is great for visual testing, but the real power comes from programmatic interaction. The inspector also has a powerful CLI mode.

Let's start by asking the server what tools it has, just like the UI did.

npx @modelcontextprotocol/inspector --cli http://localhost:3001/mcp --method tools/list

This command sends a tools/list request. You'll get back a clean JSON response describing all available tools. This is the "menu" I was talking about.

{
  "tools": [
    {
      "name": "AddNumbers",
      "description": "Add two numbers together.",
      "inputSchema": {
        "type": "object",
        "properties": {
          "a": { "description": "The first number", "type": "integer" },
          "b": { "description": "The second number", "type": "integer" }
        },
        "title": "AddNumbers",
        "description": "Add two numbers together.",
        "required": [ "a", "b" ]
      }
    }
  ]
}

Now, let's call the AddNumbers tool with some arguments.

npx @modelcontextprotocol/inspector --cli http://localhost:3001/mcp --method tools/call --tool-name AddNumbers --tool-arg a=1 --tool-arg b=2

The server executes the tool and streams the response back. For this simple function, it's instantaneous.

{
  "content": [
    {
      "type": "text",
      "text": "3"
    }
  ],
  "isError": false
}

What we've just done is foundational. We've used a standard protocol to discover and execute a function on a remote server without writing any custom client-side code. Imagine this isn't just AddNumbers, but ProcessSalesData, GenerateImageFromPrompt, or ExecuteTradeStrategy. The pattern remains the same.

The Architectural Payoff: Why This Matters

So, we made a remote calculator. Why is this an architectural upgrade?

Because we've shifted from a rigid, imperative API model to a flexible, declarative one.
图示：architecture_before_after

  1. True Decoupling and Scalability: Your services are no longer monoliths with hardcoded endpoints. They are collections of self-describing capabilities. You can build an AI agent that connects to a "Tools Server" and decides at runtime which tools to use based on the tools/list response. You can add a new tool to the server, and the agent can use it immediately without a single line of client code changing.

  2. Efficiency and User Experience: HTTP Streaming eliminates the "wait for the giant blob" problem. For any process that takes more than a few milliseconds, you can provide a real-time feed of progress and results. This transforms the user experience from a passive waiting game into an interactive session.

  3. Dramatically Simplified Development: Think of the time you've spent writing and maintaining API documentation, or building bespoke clients for every microservice. MCP's self-describing nature makes services more like libraries you can inspect and use programmatically. This frees you up to focus on building core business logic, not plumbing.

By embracing MCP and HTTP Streaming, you're not just choosing a new technology; you're adopting a more resilient, scalable, and elegant architectural pattern. You're building systems that can communicate, adapt, and evolve. So next time you see a loading spinner, ask yourself: could this be a conversation instead?

Read more