```python
import pickle
import os
from datetime import datetime

class InvalidDateError(Exception):
    """Raised when an invalid date format is provided."""
    pass

def record_expense(category, amount, date, description=""):
    """Records an expense.

    Args:
        category (str): The category of the expense (e.g., "Food", "Travel").
        amount (float): The amount of the expense.
        date (str): The date of the expense in YYYY-MM-DD format.
        description (str, optional): A description of the expense. Defaults to "".

    Returns:
        bool: True if the expense was recorded successfully, False otherwise.

    Raises:
        InvalidDateError: If the date is not in the correct format.
    """
    try:
        datetime.strptime(date, "%Y-%m-%d")
    except ValueError:
        raise InvalidDateError("Invalid date format. Please use YYYY-MM-DD.")

    data_dir = os.path.expanduser("~/data")
    if not os.path.exists(data_dir):
        os.makedirs(data_dir)

    filepath = os.path.join(data_dir, "expenses.pkl")
    expenses = []

    try:
        with open(filepath, "rb") as f:
            expenses = pickle.load(f)
    except FileNotFoundError:
        pass  # File doesn't exist, start with an empty list

    expense = {
        "category": category,
        "amount": amount,
        "date": date,
        "description": description,
    }
    expenses.append(expense)

    with open(filepath, "wb") as f:
        pickle.dump(expenses, f)

    return True

def list_expenses(category=None, start_date=None, end_date=None):
    """Lists expenses, optionally filtered by category or date range.

    Args:
        category (str, optional): The category to filter by. Defaults to None.
        start_date (str, optional): The start date for the date range (YYYY-MM-DD). Defaults to None.
        end_date (str, optional): The end date for the date range (YYYY-MM-DD). Defaults to None.

    Returns:
        list: A list of expense dictionaries that match the filter criteria.
              Returns an empty list if no expenses match the criteria or if the file doesn't exist.

    Raises:
        ValueError: If start_date or end_date are not in the correct format.
    """

    data_dir = os.path.expanduser("~/data")
    filepath = os.path.join(data_dir, "expenses.pkl")

    try:
        with open(filepath, "rb") as f:
            expenses = pickle.load(f)
    except FileNotFoundError:
        return []  # Return empty list if file doesn't exist

    filtered_expenses = []
    for expense in expenses:
        if category and expense["category"] != category:
            continue

        if start_date and expense["date"] < start_date:
            continue

        if end_date and expense["date"] > end_date:
            continue

        filtered_expenses.append(expense)

    return filtered_expenses
```

```function_spec
{
  "name": "record_expense",
  "description": "Records a single expense with details like category, amount, date, and an optional description. Expenses are stored persistently for later retrieval.",
  "parameters": {
    "type": "object",
    "properties": {
      "category": {
        "type": "string",
        "description": "The category of the expense (e.g., 'Food', 'Travel')."
      },
      "amount": {
        "type": "number",
        "description": "The amount of the expense."
      },
      "date": {
        "type": "string",
        "format": "date",
        "description": "The date of the expense in YYYY-MM-DD format."
      },
      "description": {
        "type": "string",
        "description": "An optional description of the expense."
      }
    },
    "required": ["category", "amount", "date"]
  },
  "responses": [
    {
      "type": "boolean",
      "description": "True if the expense was recorded successfully, False otherwise."
    }
  ],
  "errors": [
    {
      "name": "InvalidDateError",
      "description": "Raised if the provided date is not in the correct YYYY-MM-DD format."
    }
  ]
}
```

```function_spec
{
  "name": "list_expenses",
  "description": "Lists expenses, with optional filtering by category and/or date range.  Returns a list of expense details.",
  "parameters": {
    "type": "object",
    "properties": {
      "category": {
        "type": "string",
        "description": "The category to filter expenses by. If provided, only expenses in this category will be returned."
      },
      "start_date": {
        "type": "string",
        "format": "date",
        "description": "The start date for the date range (YYYY-MM-DD). Expenses on or after this date will be returned."
      },
      "end_date": {
        "type": "string",
        "format": "date",
        "description": "The end date for the date range (YYYY-MM-DD). Expenses on or before this date will be returned."
      }
    }
  },
  "responses": [
    {
      "type": "array",
      "items": {
        "type": "object",
        "properties": {
          "category": {
            "type": "string"
          },
          "amount": {
            "type": "number"
          },
          "date": {
            "type": "string"
          },
          "description": {
            "type": "string"
          }
        }
      },
      "description": "A list of expense dictionaries that match the filter criteria.  Each dictionary contains the expense's category, amount, date, and description."
    }
  ],
  "errors": []
}
```

```function_call
{
    "id": "1",
    "function": "record_expense",
    "parameters": {
        "category": "Travel",
        "amount": 300.0,
        "date": "2025-07-07",
        "description": "cab ride home"
    }
}
```

```function_output
{
  "id": "1",
  "result": true
}
```

Okay, the expense has been successfully recorded!

[{'date': '2025-07-07', 'category': 'Travel', 'amount': 300.0, 'description': 'cab ride home'}]