同一份工具参数里写了两次金额，为什么校验看不出来？

"""Run with Python 3.14; standard library only; no external tool calls."""
import json


def reject_duplicate_names(pairs):
    result = {}
    for key, value in pairs:
        if key in result:
            raise ValueError(f"duplicate member: {key}")
        result[key] = value
    return result


def load_unique(text):
    # This adds a duplicate-name policy, not every possible JSON policy.
    return json.loads(text, object_pairs_hook=reject_duplicate_names)


def rejects(text):
    try:
        load_unique(text)
    except ValueError as exc:
        return str(exc)
    raise AssertionError("expected a duplicate-name rejection")


def main():
    raw = '{"amount":100,"amount":900}'
    escaped = r'{"amount":100,"am\u006funt":900}'
    reversed_raw = '{"amount":900,"amount":100}'
    ordinary = json.loads(raw)
    # This is a tiny shape check, not a JSON Schema implementation.
    shape_ok = (set(ordinary) == {"amount"}
                and type(ordinary["amount"]) is int
                and 1 <= ordinary["amount"] <= 1000)
    print("default amount:", ordinary["amount"])
    print("reversed amount:", json.loads(reversed_raw)["amount"])
    print("parsed shape check:", shape_ok)
    print("duplicate policy:", rejects(raw))
    print("escaped-name policy:", rejects(escaped))
    print("nested policy:", rejects('{"request":{"amount":1,"amount":2}}'))
    print("same-value policy:", rejects('{"amount":100,"amount":100}'))
    separate = load_unique('{"a":{"amount":1},"b":{"amount":2}}')
    print("different objects:", separate["a"]["amount"], separate["b"]["amount"])
    seen_by_object_hook = []
    json.loads(raw, object_hook=lambda obj: seen_by_object_hook.append(len(obj)))
    print("members visible to object_hook:", seen_by_object_hook)
    assert ordinary == {"amount": 900} and shape_ok
    assert json.loads(escaped) == ordinary
    assert json.loads(reversed_raw) == {"amount": 100}
    assert separate == {"a": {"amount": 1}, "b": {"amount": 2}}
    assert seen_by_object_hook == [1]
    print("checks: passed")


if __name__ == "__main__":
    main()