> For the complete documentation index, see [llms.txt](https://en.help.firstline.cc/llms.txt). Markdown versions of documentation pages are available by appending `.md` to page URLs; this page is available as [Markdown](https://en.help.firstline.cc/developer/api/advanced.md).

# Advanced

- [Send message](https://en.help.firstline.cc/developer/api/advanced/send-message.md)
- [Send message via PUSH API](https://en.help.firstline.cc/developer/api/advanced/send-message/push-message.md)
- [Get Text-Call ID via hash](https://en.help.firstline.cc/developer/api/advanced/restore-text-call-id.md)
- [Send message via Text Call ID](https://en.help.firstline.cc/developer/api/advanced/send-message-via-text-call-id.md)
- [Headless Conversation API](https://en.help.firstline.cc/developer/api/advanced/headless-conversation-api.md): Use the Headless Conversation API to send customer messages from your company’s own systems, receive replies, and handle conversation events.