I see MCP as fundamentally limited: even if we had an LLM that knew how to use it perfectly, at the end of the day MCP workflows are integrations between many different APIs that were not designed to be composed and to work together.

What if $TOOL_X needs $DATA to be called, but $TOOL_Y only returns $DATA_SUBSET? What happens when $TOOL_Z fails mid-workflow, after $TOOL_W has already executed?