Twitter is now allowing developers to add any kind of metadata they want to tweets authored in their apps, using a system called “Annotations.”

Metadata, loosely defined, is data about data — for example, information on where a tweet came from or what time it was sent.

Annotations will let developers make up what kind of data they want to add to a tweet.

This could be huge, or it could be a mess depending on what kinds of metadata third-party apps add to tweets. For example, if a developer adds one type of metadata to a tweet, how will another app be able to recognize and interpret it? Twitter’s director of platform, Ryan Sarver, said the company was working on a list of recommended types of metadata, but that it wouldn’t be strict.

“We want to see what comes from the community,” he said.

Twitter is probably betting that certain kinds of popular metadata will naturally emerge. This is what happened with retweets, which just became part of Twitter etiquette over time and were ultimately adopted by the company through an official retweet function.