Using a chatbot to make a simple story

Hi

I’m trying to get a chatbot to write a 50 word (could be less) story about a cat that only use the words my, the and I, or words that only use the letters s, a, t, p, i, n

Am I asking the right question? Am I missing out another instruction?

I tried in Writesonic and it included many other words, tried Chat gpt and it didn’t do anything.

Thanks in advance