aspnetcore-debugger-mcp

Install & configure

Once per machine: install the tool. Once per project: register it. Then just chat.

Step 1 — Install the MCP server (once per machine)

Needs the .NET 10 SDK (download).

dotnet tool install -g AspNetCoreDebuggerMcp --prerelease

--prerelease is needed while the version is 0.x (or any -preview/-rc suffix). Drop it once a stable 1.0.0 ships.

The package ships prebuilt netcoredbg (Samsung’s MIT-licensed .NET debugger) for linux-x64, linux-arm64, win-x64, osx-x64, osx-arm64. The tool auto-detects your platform at startup — no separate install needed.

That puts the aspnetcore-debugger-mcp binary on your PATH. Verify:

aspnetcore-debugger-mcp
# starts and idles on stdin; Ctrl-C to exit

If it errors with “netcoredbg not found”, see Troubleshooting below.

Step 2 — Register with your MCP client (once per project, or globally)

Claude Code

Either CLI:

claude mcp add aspnetcore-debugger -- aspnetcore-debugger-mcp

Or edit .mcp.json (project) / ~/.claude.json (global):

{
  "mcpServers": {
    "aspnetcore-debugger": {
      "command": "aspnetcore-debugger-mcp"
    }
  }
}

Claude Desktop

Edit claude_desktop_config.json — same JSON shape goes in the mcpServers block:

{
  "mcpServers": {
    "aspnetcore-debugger": {
      "command": "aspnetcore-debugger-mcp"
    }
  }
}

Restart Claude Desktop after editing.

Step 3 — Just chat with Claude

Open Claude Code or Claude Desktop in your .NET project. Run /mcp — aspnetcore-debugger should show as connected.

From here, don’t invoke the tools yourself. Just describe what you want:

“Debug my API and figure out why GET /users/42 returns null.”

Claude picks the right tools (debug_launch, breakpoint_set, variables_get, etc.) and reports back what it actually saw at runtime. See the worked examples for the patterns this enables.

Updating

dotnet tool update -g AspNetCoreDebuggerMcp --prerelease

Uninstalling

dotnet tool uninstall -g AspNetCoreDebuggerMcp

Then remove the aspnetcore-debugger entry from your MCP client config.

Using a custom netcoredbg build

The bundled binary is pinned to a specific Samsung release. If you need to use a custom build (e.g. a newer Samsung release, a patched binary, or an unbundled architecture), set NETCOREDBG_PATH:

{
  "mcpServers": {
    "aspnetcore-debugger": {
      "command": "aspnetcore-debugger-mcp",
      "env": { "NETCOREDBG_PATH": "/absolute/path/to/netcoredbg" }
    }
  }
}

The env var wins over the bundled binary. See macOS arm64 — building netcoredbg if you want to build your own.

Troubleshooting

Symptom	Likely cause
/mcp shows the server as failed / disconnected	The aspnetcore-debugger-mcp binary isn’t on PATH. Run the verify command from Step 1 in a regular shell.
Tool calls error with “netcoredbg not found”	The bundled binary for your RID couldn’t be found — your platform may not be one of the five we bundle. Set NETCOREDBG_PATH to a binary you’ve built or downloaded.
Trace tool errors with “user breakpoints exist”	Trace mode requires no user BPs — call breakpoint_remove on each first, or trace_stop if a previous trace is still active.

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