One advantage is the MCP advertises itself to the agent with its schema and api shape. Unless your CLI is in the corpus with lots of examples the agent has to learn every time. Skills help a little bit but I find the recall on skills pretty low. However I also find codex will reliably use MCPs advertised while Claude always reaches for tools like Bash() likely because it’s aligned so heavily on its own tools and is very hard to get to use an MCP if literally any Bash() approach is possible, including breaking glass to find creds, even when an MCP is clearly advertised in CLAUDE.md, skills, and explicit user instruction. I find it fascinating that Anthropic makes a product that seems to be really poor at following instructions and OpenAI seems to generally follow guard rails.