backend/tools/calculator_tool.py

import ast, operator as op
_OPS = {ast.Add: op.add, ast.Sub: op.sub, ast.Mult: op.mul, ast.Div: op.truediv,
        ast.Pow: op.pow, ast.USub: op.neg, ast.Mod: op.mod}


def _ev(node):
    if isinstance(node, ast.Num):       return node.n
    if isinstance(node, ast.Constant):  return node.value
    if isinstance(node, ast.BinOp):     return _OPS[type(node.op)](_ev(node.left), _ev(node.right))
    if isinstance(node, ast.UnaryOp):   return _OPS[type(node.op)](_ev(node.operand))
    raise ValueError("unsafe expression")


def run(params: dict) -> dict:
    expr = params.get("expression", "")
    try:
        return {"result": _ev(ast.parse(expr, mode="eval").body), "expression": expr}
    except Exception as e:
        return {"error": str(e), "expression": expr}