What is the best way to elicit a response from a device using an http call?
Check out the Internet-to-agent (HTTP) and agent-to-device recipes in the Dev Center’s sample code section. These will show you how the agent can manage incoming HTTP requests and, as necessary, communicate with the device. Devices don’t communicate with external HTTP requests directly, for security reasons.
If it’s just the agent-device comms you’re interested in, then the appropriate recipe should help you there.