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skills/claude-agent-sdk/examples/mcp_calculator.py

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+#!/usr/bin/env python3
+"""Example: Calculator MCP Server.
+
+This example demonstrates how to create an in-process MCP server with
+calculator tools using the Claude Code Python SDK.
+
+Unlike external MCP servers that require separate processes, this server
+runs directly within your Python application, providing better performance
+and simpler deployment.
+"""
+
+import asyncio
+from typing import Any
+
+from claude_agent_sdk import (
+    ClaudeAgentOptions,
+    create_sdk_mcp_server,
+    tool,
+)
+
+# Define calculator tools using the @tool decorator
+
+
+@tool("add", "Add two numbers", {"a": float, "b": float})
+async def add_numbers(args: dict[str, Any]) -> dict[str, Any]:
+    """Add two numbers together."""
+    result = args["a"] + args["b"]
+    return {
+        "content": [{"type": "text", "text": f"{args['a']} + {args['b']} = {result}"}]
+    }
+
+
+@tool("subtract", "Subtract one number from another", {"a": float, "b": float})
+async def subtract_numbers(args: dict[str, Any]) -> dict[str, Any]:
+    """Subtract b from a."""
+    result = args["a"] - args["b"]
+    return {
+        "content": [{"type": "text", "text": f"{args['a']} - {args['b']} = {result}"}]
+    }
+
+
+@tool("multiply", "Multiply two numbers", {"a": float, "b": float})
+async def multiply_numbers(args: dict[str, Any]) -> dict[str, Any]:
+    """Multiply two numbers."""
+    result = args["a"] * args["b"]
+    return {
+        "content": [{"type": "text", "text": f"{args['a']} × {args['b']} = {result}"}]
+    }
+
+
+@tool("divide", "Divide one number by another", {"a": float, "b": float})
+async def divide_numbers(args: dict[str, Any]) -> dict[str, Any]:
+    """Divide a by b."""
+    if args["b"] == 0:
+        return {
+            "content": [
+                {"type": "text", "text": "Error: Division by zero is not allowed"}
+            ],
+            "is_error": True,
+        }
+
+    result = args["a"] / args["b"]
+    return {
+        "content": [{"type": "text", "text": f"{args['a']} ÷ {args['b']} = {result}"}]
+    }
+
+
+@tool("sqrt", "Calculate square root", {"n": float})
+async def square_root(args: dict[str, Any]) -> dict[str, Any]:
+    """Calculate the square root of a number."""
+    n = args["n"]
+    if n < 0:
+        return {
+            "content": [
+                {
+                    "type": "text",
+                    "text": f"Error: Cannot calculate square root of negative number {n}",
+                }
+            ],
+            "is_error": True,
+        }
+
+    import math
+
+    result = math.sqrt(n)
+    return {"content": [{"type": "text", "text": f"√{n} = {result}"}]}
+
+
+@tool("power", "Raise a number to a power", {"base": float, "exponent": float})
+async def power(args: dict[str, Any]) -> dict[str, Any]:
+    """Raise base to the exponent power."""
+    result = args["base"] ** args["exponent"]
+    return {
+        "content": [
+            {"type": "text", "text": f"{args['base']}^{args['exponent']} = {result}"}
+        ]
+    }
+
+
+def display_message(msg):
+    """Display message content in a clean format."""
+    from claude_agent_sdk import (
+        AssistantMessage,
+        ResultMessage,
+        SystemMessage,
+        TextBlock,
+        ToolResultBlock,
+        ToolUseBlock,
+        UserMessage,
+    )
+
+    if isinstance(msg, UserMessage):
+        for block in msg.content:
+            if isinstance(block, TextBlock):
+                print(f"User: {block.text}")
+            elif isinstance(block, ToolResultBlock):
+                print(
+                    f"Tool Result: {block.content[:100] if block.content else 'None'}..."
+                )
+    elif isinstance(msg, AssistantMessage):
+        for block in msg.content:
+            if isinstance(block, TextBlock):
+                print(f"Claude: {block.text}")
+            elif isinstance(block, ToolUseBlock):
+                print(f"Using tool: {block.name}")
+                # Show tool inputs for calculator
+                if block.input:
+                    print(f"  Input: {block.input}")
+    elif isinstance(msg, SystemMessage):
+        # Ignore system messages
+        pass
+    elif isinstance(msg, ResultMessage):
+        print("Result ended")
+        if msg.total_cost_usd:
+            print(f"Cost: ${msg.total_cost_usd:.6f}")
+
+
+async def main():
+    """Run example calculations using the SDK MCP server with streaming client."""
+    from claude_agent_sdk import ClaudeSDKClient
+
+    # Create the calculator server with all tools
+    calculator = create_sdk_mcp_server(
+        name="calculator",
+        version="2.0.0",
+        tools=[
+            add_numbers,
+            subtract_numbers,
+            multiply_numbers,
+            divide_numbers,
+            square_root,
+            power,
+        ],
+    )
+
+    # Configure Claude to use the calculator server with allowed tools
+    # Pre-approve all calculator MCP tools so they can be used without permission prompts
+    options = ClaudeAgentOptions(
+        mcp_servers={"calc": calculator},
+        allowed_tools=[
+            "mcp__calc__add",
+            "mcp__calc__subtract",
+            "mcp__calc__multiply",
+            "mcp__calc__divide",
+            "mcp__calc__sqrt",
+            "mcp__calc__power",
+        ],
+    )
+
+    # Example prompts to demonstrate calculator usage
+    prompts = [
+        "List your tools",
+        "Calculate 15 + 27",
+        "What is 100 divided by 7?",
+        "Calculate the square root of 144",
+        "What is 2 raised to the power of 8?",
+        "Calculate (12 + 8) * 3 - 10",  # Complex calculation
+    ]
+
+    for prompt in prompts:
+        print(f"\n{'=' * 50}")
+        print(f"Prompt: {prompt}")
+        print(f"{'=' * 50}")
+
+        async with ClaudeSDKClient(options=options) as client:
+            await client.query(prompt)
+
+            async for message in client.receive_response():
+                display_message(message)
+
+
+if __name__ == "__main__":
+    asyncio.run(main())