What works fine without it
- Drafting messages, descriptions and proposals.
- Summarizing calls, emails and long documents.
- Answering questions from documentation.
- Classifying or extracting information from text.
What does not work without tool execution
- Creating a customer, job, estimate or invoice.
- Sending a contract for signature.
- Booking or moving an appointment against real availability.
- Reading an accurate count or total from live data.
- Starting the next step of a workflow.
Are there alternatives to MCP?
Yes — proprietary function calling, in-house tool layers, and bespoke integrations all achieve execution. The trade-off is portability and maintenance: each assistant needs its own wiring, and each new capability multiplies that work.
MCP matters because it standardizes the contract, not because it is the only way.