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Testing your MCP server with Visual Studio HTTP Files

If you're building or testing Model Context Protocol (MCP) servers and you need a quick way to verify your endpoints are working correctly. Visual Studio's HTTP files (.http) provide an elegant, code-based approach to API testing

What are Visual Studio HTTP files?

HTTP files are plain text files with a .http or .rest extension that let you define and execute HTTP requests directly in your editor. They're supported in Visual Studio, Visual Studio Code (with the REST Client extension), and JetBrains IDEs. Think of them as executable documentation for your API.

Why use HTTP files for MCP testing?

The Model Context Protocol defines a JSON-RPC 2.0 interface for AI model interactions. Testing these endpoints traditionally meant using tools like Postman or curl commands, but HTTP files offer several advantages:

  • Version control friendly: Store your test requests alongside your code
  • Easy sharing: Team members can run the same tests instantly
  • Fast iteration: Make changes and re-run with a single click
  • Environment variables: Switch between dev, staging, and production easily
  • No external tools needed: Everything lives in your IDE

Setting up a basic HTTP file for MCP testing

Create a new file called mcp-tests.http in your project.

Here's a basic structure for testing an MCP server:

Tips for MCP-specific testing

  1. Start with initialization: Always test the initialize endpoint first to ensure your MCP server handshake works correctly.
  2. Test capability negotiation: Verify that your server correctly responds to different client capabilities.
  3. Validate JSON-RPC format: MCP uses JSON-RPC 2.0, so ensure all responses include jsonrpc, id, and either result or error.
  4. Test all tool parameters: For each tool your MCP server exposes, create tests with valid, invalid, and edge-case parameters.

Happy testing!

More information

Use environment specific variables in HTTP files

Use .http files in Visual Studio 2022 | Microsoft Learn

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