I often just put direct curl commands in a skill, the agent uses that, and it works perfectly for custom API integrations. Agents are perfectly capable of doing these types of things, and it means the LLM just uses a flexible set of tools to achieve almost anything.
I think this is the best of both worlds. Design a sane API (that is easy to consume for both humans and agents), then teach the agents to use it with a skill.
But I agree with the author on custom CLI tooling. I don’t want to install another opaque binary on my machine just to call some API endpoints.
Obviously opaque binaries are hardly an improvement over MCP, but providing a few curl + jq oneliners to interact with a REST API works great in my experience. Also means no external scripts, just a single markdown file.
With a good CLI, an agent may be able to do something outside of the scope of it's skill fairly easily, by running help commands or similar. With even a well written API it is not as easy.
I suppose that curl + API docs could replace a CLI but that's really token inefficient