DnSpy-MCPserver-Extension

# AgentSmithers dnSpyEx MCPServer Extension This is a dnSpy MCPServer Extension for the use of automated AI .NET reverse engineering The \dnSpy\Extensions\Examples\AgentSmithers dnSpy MCPServer.Extension has been updated to include the MCPServer logic with a few starting function to feed the decompiled code back to the LLM. This is an ongoing project and I plan to continue to add commands as time persist. To execute the server, run as Administrator so the the Http server may Listen on +:3001 (release is currently set to 3003) and *:50301 for the streamable MCP Server. The following command will suffice: # Recommended debug workflow: Step 1: Ensure dnSpy is set as Startup Project Step 2: Open Launch Settings In Solution Explorer, right-click on your project Select Properties In the left sidebar, click on Debug (or Debugging) Then go to "Open debug launch profiles UI" Step 3: Add Command Line Arguments In the Command line arguments text box, enter: --extension-directory "$(SolutionDir)Extensions\Examples\Example1.Extension\bin\Debug\net48" Step 4: Save Click Save or press Ctrl+S Close the properties window Step 5: Test Press F5 or click the green play button Your dnSpy should now launch with your extension loaded! # OR cd {dnspy directory} dnspy.exe --extension-directory {Path to extension} Example 1: dnspy.exe --extension-directory "C:\repos\dnSpy\Extensions\Examples\Example1.Extension\bin\Debug\net48" Example 2 in CMD: C:\Users\user>"C:\Users\user\source\repos\DnSpy-MCPserver-Extension\dnSpy\dnSpy\bin\Debug\net48\dnspy.exe" --extension-directory "C:\Users\user\source\repos\DnSpy-MCPserver-Extension\dnSpy\dnSpy\bin\Debug\net48\Extensions" # OR In alternative you may copy the release into the Extension folder within the dnSpy\Extensions\AgentSmithersMCPServer path. ## Modifying the project Ensure to compile the primary DnSpy Soultion (Clean and rebuild) so that the dependancies for "AgentSmithers DnSpyEx MCPServer" can use them for its own build. (Note: When compiling DnSpyEx you may have approx. ~20 errors, this will not prevent the 45 Projects from compiling) <img width="846" alt="image" src="https://github.com/user-attachments/assets/4d9269fa-ab0e-4392-8042-f79b31795e43" /> <img width="991" alt="image" src="https://github.com/user-attachments/assets/57e708b3-05e9-4edd-8b72-53c0850c5304" /> Once dnSpy is fully cleaned and compiled, navigate to the Example1 Extension Project. In there is the modified code. Make your adjustments, compile then use the --extension-directory argument when executing DnSpy.exe to point to your projects extension path. In alternative you may pull down the latest dnSpyEx then rename the Extension sample folder to another name and bring the modified extension folder over to recompile. ## Compiling Clean and rebuild (I used visual Studio 2026, I think you'll need .NET Framework 4.8 and Core 10 Installed to compile the full solution) #Clearing the errors above upon inital IDE load - Not executing these steps may result in the error below. HKEY_LOCAL_MACHINE\SYSTEM\CurrentControlSet\Control\FileSystem Find the value LongPathsEnabled. Double-click it and change the value to 1. Restart your computer (or at least restart Visual Studio). Argument 1: cannot convert from 'System.ReadOnlySpan<char>' to 'string' Cannot implicitly convert type 'System.ReadOnlySpan<char>' to 'string' Argument 1: cannot convert from 'System.ReadOnlySpan<char>' to 'string' Argument 1: cannot convert from 'System.ReadOnlySpan<char>' to 'string' foreach statement cannot operate on variables of type 'void' because 'void' does not contain a public instance or extension definition for 'GetEnumerator' Metadata file 'C:\Users\User\source\repos\DnSpy-MCPserver-Extension\dnSpy\dnSpy\obj\Debug\net48\ref\dnSpy.exe' could not be found Metadata file 'C:\Users\User\source\repos\DnSpy-MCPserver-Extension\dnSpy\dnSpy\obj\Debug\net8.0-windows\ref\dnSpy.dll' could not be found # Supported commands Currently readonly commands are supported to enumerate active namespaces, classes and functions by the AI. Plans are in the works to allow the AI to make interactive adjustments to the decompiled assemblies. ``` Get_Selected_Node - Gets the currently selected node within dnSpyEx Get_Loaded_Assemblies - Gets all Assemblys currently loaded within dnSpyEx Namespaces_From_Assembly - Dumps all unique namespaces under a given Assembly Classes_From_Namespace - List all Classes under a given Namespace Get_Class_Sourcecode - Dumps a target Class sourcecode Get_Method_Prototypes - List all Method prototypes from a given Class within a given Namespace Get_Method_SourceCode - Dumps a target Method's sourcecode Update_Method_SourceCode - Update a target Method's sourcecode Get_Function_Opcodes - Returns the IL opcodes of the specified method (with source line numbers) Set_Function_Opcodes - Modifies the IL of the specified method at a given IL line index Update_Tabs_View - Update all active tabs to reflect any changes or adjustments Rename_Namespace - Renames exactly one distinct namespace across all types Rename_Class - Renames a specific class within a given Namespace Rename_Method - Renames a specific Methods by Class within a given Namespace These commands allow you to inspect and modify .NET assemblies loaded in dnSpyEx, including viewing and editing source code, IL code, and performing various renaming operations. ``` # Once the extension is loaded A messagebox will appear allowing you a chance to attach your debugger if nessessary  Click "OK" and the MCPServer will load on :3001 Connect via SSE or if your application only supports STDIO (Claude Desktop / Windsurf) grab a copy of the STDIO<->SSE bridge https://github.com/AgentSmithers/MCPProxy-STDIO-to-SSE Attach the Bridge AFTER hitting "OK" and your good to go.