Try this
- Offer answer sizes before asking the personal question, so a short reply is an agreed format rather than an apparent refusal.
- Answer at the chosen size yourself if you are both participating. Leave follow-up questions for a separate invitation.
A worked example
“I can manage one sentence tonight. Could that be enough for today?”
An invented example to adapt, not a real exchange or a script you have to follow.
Before you leave it here
Do not turn a short answer into an invitation to demand the missing details.