Build Email Sending Tool Agent Tools

You are building AI agent tools. Define the Email Sending Tool tool specification.

For each tool provide:
1. Function name and description
2. Parameters with types and descriptions
3. Return value specification
4. Implementation code (Python)
5. Error handling
6. Rate limiting considerations
7. Security considerations
8. Example usage in an agent conversation

Format: OpenAI function-calling schema compatible.

Agent context: {context}