README

MCPFramework4D

Model Context Protocol for Pascal developers.

MCPFramework4D helps you build MCP servers and clients in Delphi 11+ and Lazarus/FPC on Windows, with IDE components, project templates, and sample apps ready for Claude Desktop testing.

Why this project

• Build MCP servers over stdio
• Call local MCP servers from Delphi or Lazarus apps
• Add MCP support to legacy desktop applications through non-visual components
• Start faster with Delphi and Lazarus project wizards

First-glance feature summary

Supported MCP surface

Currently implemented and tested around the local Windows workflow:

• initialize
• notifications/initialized
• ping
• tools/list
• tools/call
• protocol version negotiation

Supported protocol versions:

• 2025-11-25
• 2025-06-18
• 2025-03-26
• 2024-11-05

Packages and IDE integration

Delphi

• Runtime package: package\MCPFramework4D.dproj
• Design-time package: package\MCPFramework4DDesign.dproj
• Workspace: MCPFramework4D_GroupProject.groupproj

After installing the design-time package, RAD Studio adds:

• Tool Palette page: MCPFramework4D

• Components: TMCPServerComponent, TMCPServerHostComponent, TMCPClientComponent

  

• New Project entries:

  • MCP Server Project
  • MCP Client Project

Lazarus

• Runtime package: lazarus\MCPFramework4DRuntime.lpk
• Design-time package: lazarus\MCPFramework4DDesign.lpk

After installing the design-time package, Lazarus adds:

• Component palette page: MCPFramework4D
• Components: TMCPServerComponent, TMCPServerHostComponent, TMCPClientComponent

• New Project category: MCPFramework4D

Programming model

Delphi 11+

Delphi uses attribute-based tool registration.

[MCPTool('sample', 'Sample tools')]
TSampleTools = class
public
  [MCPToolMethod('echo', 'Echo a message back')]
  function Echo([MCPToolParam('Message to echo back')] const Text: string): string;
end;

Lazarus / FPC

Lazarus uses explicit descriptor registration.

procedure RegisterMyTool;
var
  LDescriptor: TMCPToolDescriptor;
begin
  LDescriptor := TMCPToolDescriptor.Create('sample', 'Sample tools', TSampleTools);
  with LDescriptor.AddMethod('Echo', 'echo', 'Echo a message back', @InvokeEcho) do
    AddParameter('Text', 'Message to echo back', 'string');
  TMCPToolRegistry.GetInstance.RegisterToolDescriptor(LDescriptor);
end;

Main components

TMCPServerComponent

Use this to expose tools and server metadata from an existing application.

Main capabilities:

• register tools
• handle messages
• run a server over stdio

TMCPServerHostComponent

Use this to host a TMCPServerComponent over a selected transport.

Main capabilities:

• start and stop hosting
• stdio hosting in Delphi and Lazarus
• HTTP/HTTPS hosting in Delphi

Note: in Lazarus/FPC, mtHttp currently raises a clear runtime error and is intentionally not enabled yet.

TMCPClientComponent

Use this to connect to and call another MCP server.

Main capabilities:

• connect and disconnect
• list tools
• call tools
• ping

Note: in Lazarus/FPC, TMCPClientComponent currently supports mtStdio. HTTP transport is still Delphi-only.

Samples

The repo includes practical samples instead of toy-only demos:

• src\Samples\SimpleServer
• src\Samples\SimpleClient
• src\Samples\VclServerDemo

The sample server exposes system-style tools such as:

• machine overview
• memory information
• drive information
• OS information

The VCL demo can run as a normal visible app or be launched by Claude Desktop as an MCP server.

Claude Desktop quick start

Example config:

{
  "mcpServers": {
    "mcpframework4d-sample": {
      "command": "D:\\path\\to\\YourServer.exe",
      "args": []
    }
  }
}

Suggested test prompt:

List the available MCP tools, call one safe sample tool, and summarize whether the server connection is working correctly.

There are also ready-to-edit sample config files in the repository for the included demos.

Build notes

• Windows-focused
• stdio first
• no third-party Delphi dependency required for the core stdio workflow
• Delphi HTTP/S hosting uses Indy units that ship with RAD Studio
• package outputs are separated by compiler/platform/config to reduce cross-version conflicts

Compatibility

• Delphi 11 Alexandria and newer
• Lazarus with Free Pascal on Windows

Common Delphi package issue

If you see something like:

Bad packaged unit format ... Expected version ... Found version ...

you are usually loading package binaries from a different Delphi version.

Typical fix:

1. Close the IDE.
2. Delete old generated outputs such as package\build, *.dcp, *.bpl, Win32, Win64, *.identcache, and *.local.
3. Rebuild the runtime package first.
4. Rebuild the design-time package second.

Status

This repository is now set up as a dual-purpose Delphi and Lazarus MCP framework with:

• shared runtime code
• IDE components in both environments
• project wizards in both environments
• sample applications for local Claude Desktop testing

Made with :heart: on Delphi