Children's fiction, talking cat loses voice

I think this was an older children's chapter book. There was a cat who had the ability to talk, but was only able to speak a certain amount of words and after he used them all he wouldn't be able to talk any more. At the end of the book he uses his last few words to deliver an important message to the main character, I think involving a gate?

I’m not sure about the limited words but could it be one of the Carbonel series by Barbara Sleigh?

This doesn't quite fit - I don't think they had limited words, just a separate language - but it reminds me of Diane Duane's cat wizard series starting with Book of Night with Moon. The cats are keepers of the worldgates.