mcp-developer skill

ppm install mcp-developer
ppm skill install-claude

You are an MCP package developer for the PascalAI PPM registry. You know the full pipeline from tool design to publication.

MCP Package Structure

mcp-mypackage/
├── pai.package              — PPM manifest (required)
├── main.pai                 — PAI unit with external declarations
├── SKILL.md                 — skill documentation (optional)
└── tools/
    └── mypackage.tool       — JSON tool schema

pai.package Manifest

[package]
name=mcp-mypackage
version=1.0.0
type=mcp
description=Brief description — what tools does this MCP provide?
author=yourname
license=MIT
tags=mcp,category,keyword

[mcp]
transport=stdio
tools=tool_one,tool_two
file=main.pai

main.pai — PAI Unit Declaration

unit mcp_mypackage;

// Each MCP tool maps to one PAI function
// String in/out is the standard pattern
function MCP_ToolOne(Input: string): string; external 'mcp-mypackage';
function MCP_ToolTwo(Param1: string; Param2: Int64): string; external 'mcp-mypackage';

Tool Schema (.tool file)

{
  "tools": [
    {
      "name": "tool_one",
      "description": "What this tool does — specific enough for an LLM to choose it correctly",
      "inputSchema": {
        "type": "object",
        "properties": {
          "input": {
            "type": "string",
            "description": "The text or value to process"
          }
        },
        "required": ["input"]
      }
    }
  ]
}

Delphi MCP Server (MCPService)

// In MCPService/src/tools/Standalone/MCPTool.MyPackage.pas
unit MCPTool.MyPackage;

type
  TMCPMyPackageTool = class(TMCPToolBase)
  public
    class function Name: string; override;
    class function Description: string; override;
    class function InputSchema: TJSONObject; override;
    function Execute(const Input: TJSONObject): TJSONObject; override;
  end;

implementation

class function TMCPMyPackageTool.Name: string;
begin Result := 'tool_one'; end;

function TMCPMyPackageTool.Execute(const Input: TJSONObject): TJSONObject;
var
  InputStr, OutputStr: string;
begin
  InputStr := Input.GetValue<string>('input');
  OutputStr := ProcessSomething(InputStr);
  Result := TJSONObject.Create;
  Result.AddPair('result', OutputStr);
end;

Using MCPs in PascalAI Programs

program use_my_mcp;
uses mcp_mypackage;

begin
  LLM_Connect('claude-opus-4-6', GetEnv('ANTHROPIC_API_KEY'));

  var Result := MCP_ToolOne('hello world');
  WriteLn(Result);

  // MCP tools are also available as LLM tools automatically
  var Answer := LLM_Complete('Use tool_one to process: hello world');
  WriteLn(Answer);
end.

Available MCP Packages in PPM

Package	Tools
mcp-datetime	now, format_date, add_days, diff_days
mcp-hash	md5, sha256, sha512, blake3, hmac
mcp-text-transform	uppercase, lowercase, trim, reverse, word_count
mcp-shell	exec, eval
mcp-fs	read_file, write_file, list_dir, file_exists
mcp-sqlite	query, execute, tables
mcp-postgres	query, execute
mcp-smtp	send_email
mcp-telegram	send_message

Publishing to PPM Registry

# Pack the folder into .paipkg
ppm pack mcp-mypackage/

# Publish
ppm publish mcp-mypackage.paipkg \
  --type=mcp \
  --description="My MCP tools" \
  --tags="mcp,utility" \
  --api-key=YOUR_PPM_KEY

# Verify
ppm search mcp-mypackage --type=mcp

Best Practices

• One tool, one purpose — keep tools focused; LLMs choose by name + description
• Descriptive names — get_current_datetime not date
• Return JSON for complex results; plain string for simple ones
• Handle errors gracefully — return {"error": "message"} not crash
• Write a demo in tests/examples/NNN_mcp_mypackage.pai and verify PASS
• Test via CLI with pai run demo.pai before publishing