They already have a HTTP API, but the real reason is that CLIs are emerging as the most ergonomic way for the current wave of AI agents to do stuff. There's a few benefits over APIs:

- No need to worry about transport layer stuff at all, including auth or headers. This is baked in, so saves context.

- They are self describing with --help and then nested --help commands, way better than trying to decipher an OpenAPI spec. You usually don't even need an agent skill, just call the --help and the LLM figures it out.