1) Valid point, this could haven been wsdl/swagger. But the MCP spec supports spinning up local applications and communicate via stdio which open api cannot do.

2 + 3) having a few commands that AI knows it should call and confidently so without security concern, is better than just give AI permision to do every thing under the sun and tell it to code a program doing so.

The prompt for the later is also much more complex and does not work as predictably.