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MCP host compatibility

Wuwe's stdio server supports the two framing styles exercised by repository tests:

  • Content-Length framed JSON-RPC;
  • one JSON-RPC object per line.

The server replies using the framing style of the incoming request. Protocol version 2024-11-05 is the current Wuwe compatibility target.

Host configuration​

Build the example and use its absolute path in the host configuration:

cmake --build build-vcpkg --config Release --target mcp_stdio_example
Resolve-Path .\build-vcpkg\examples\Release\mcp_stdio_example.exe

A common desktop-host shape is:

{
  "mcpServers": {
    "wuwe": {
      "command": "D:\\path\\to\\mcp_stdio_example.exe",
      "args": []
    }
  }
}

Configuration file names and nesting differ by host. Preserve the executable, arguments, working directory, and required environment variables when adapting the entry.

Expected protocol surface​

The example exposes:

  • tools echo_text and preview_image;
  • resource wuwe://example/readme;
  • resource template wuwe://example/{name};
  • prompt echo_prompt.

A normal host sequence is:

  1. initialize;
  2. notifications/initialized;
  3. optional ping;
  4. tools/list, resources/list, resources/templates/list, and prompts/list;
  5. tool calls or resource and prompt reads.

The library also implements roots, subscriptions, list-change notifications, progress, logging, sampling, and elicitation. A host may expose only a subset of these features in its UI.

Verification​

Run the MCP unit suite and the process transcript:

ctest --test-dir build-vcpkg -C Release -R mcp --output-on-failure
.\tools\mcp-host-transcript.ps1 -ServerPath build-vcpkg\examples\Release\mcp_stdio_example.exe

Pass criteria:

  • the host starts the process without protocol text on stdout;
  • initialization succeeds;
  • listed tools, resources, templates, and prompts match the example;
  • echo_text returns its input;
  • the image result contains an image/png content item;
  • the resource can be read and the prompt can be fetched;
  • ping returns an empty result object.

For RAG verification, run knowledge_mcp_example and call search_knowledge.

Troubleshooting​

  • Prefer an absolute executable path.
  • Keep logs on stderr; stdout is the MCP transport.
  • Pass API keys and other environment values through the host's server configuration.
  • Capture raw stdin, stdout, and stderr before changing framing logic.
  • If rich content is invisible in the UI, inspect the raw MCP response; host rendering support varies.
  • Treat sampling and elicitation as negotiated capabilities. Do not assume every host will service server-initiated requests.