As agentic systems seem to mainly interoperate with REST style systems I suspect that using URIs for resource use descriptions would be more natural.
CodeAct is one way to abstract away some things, and bring others to the forefront. Especially when it comes to anything requiring a sidecar for mTLS, or something agents must be aware of, like error handling for whenever some call fails deep inside the stack. Troubleshooting access issues is key, during tool development and when using said tool in production, too. For many, many things, CodeAct is simply superior to naive calling conventions that you see around MCP clients, think OpenAPI.