Yes. Individual messages - including Shortcuts - have a character limit of 320 characters per message. If your text is longer, you'll need to break it up into multiple messages. Announcements have a character limit of 160 characters.
We have these limits in place because texting, as a medium, requires more concise messages than email. Many of your recipients' carriers might break the message up into pieces and deliver them out of order - something we cannot control - if the message is particularly long. The character limits allows us to deliver your customers the best experience the most consistently.