Add the first implementation

Author: githejie

.gitignore

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+# Python-generated files
+__pycache__/
+*.py[oc]
+build/
+dist/
+wheels/
+*.egg-info
+
+# Virtual environments
+.venv

.python-version

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+3.10

pyproject.toml

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+[project]
+name = "mcp-server-calculator"
+version = "0.1.0"
+description = "A Model Context Protocol server for calculating"
+readme = "README.md"
+requires-python = ">=3.10"
+authors = [{ name = "He Jie", email = "[email protected]" }]
+keywords = ["mcp", "llm", "math", "calculator"]
+license = { text = "MIT" }
+classifiers = [
+    "Development Status :: 4 - Beta",
+    "Intended Audience :: Developers",
+    "License :: OSI Approved :: MIT License",
+    "Programming Language :: Python :: 3",
+    "Programming Language :: Python :: 3.10",
+]
+dependencies = [
+    "mcp>=1.4.1",
+]
+
+[project.scripts]
+mcp-server-calculator = "mcp_server_calculator:main"
+
+[build-system]
+requires = ["hatchling"]
+build-backend = "hatchling.build"

src/mcp_server_calculator/__init__.py

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+from .calculator import main
+
+if __name__ == "__main__":
+    main()

src/mcp_server_calculator/__main__.py

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+from mcp_server_calculator import main
+
+main()

src/mcp_server_calculator/calculator.py

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+import ast
+import operator
+from mcp.server.fastmcp import FastMCP
+
+def evaluate(expression: str) -> str:
+    allowed_operators = {
+        ast.Add: operator.add,
+        ast.Sub: operator.sub,
+        ast.Mult: operator.mul,
+        ast.Div: operator.truediv,
+        ast.FloorDiv: operator.floordiv,
+        ast.Mod: operator.mod,
+        ast.Pow: operator.pow,
+        ast.USub: operator.neg,
+    }
+
+    def eval_expr(node):
+        if isinstance(node, ast.Constant):
+            return node.value
+        elif isinstance(node, ast.BinOp):
+            left = eval_expr(node.left)
+            right = eval_expr(node.right)
+            if type(node.op) in allowed_operators:
+                return allowed_operators[type(node.op)](left, right)
+        elif isinstance(node, ast.UnaryOp) and isinstance(node.op, ast.USub):
+            return -eval_expr(node.operand)
+        raise ValueError("Unsupported operation")
+
+    parsed_expr = ast.parse(expression, mode='eval')
+    result = eval_expr(parsed_expr.body)
+    return str(result)
+
+mcp = FastMCP("calculator")
+
+@mcp.tool()
+async def calculate(expression: str) -> str:
+    """Calculates/evaluates the given expression."""
+    return evaluate(expression)
+
+def main():
+    mcp.run()