> modern MCP clients do smart tool search that obviates the entire "I am sending the full list of tools back and forth" mode of operation

How, "Dynamic Tool Discovery"? Has this been codified anywhere? I've only see somewhat hacky implementations of this idea

https://github.com/modelcontextprotocol/modelcontextprotocol...

Or are you talking about the pressure being on the client/harnesses as in,

https://platform.claude.com/docs/en/agents-and-tools/tool-us...

More of the latter than the former. The protocol itself is constrained to a set of well-defined primitives, but clients can do a bunch of pre-processing before invoking any of them.