Raffi Krikorian, sviluppatore API Twitter, ha pubblicato sul proprio blog la mappa di un tweet in formato Json:

Notate quante informazioni siano contenute in un singolo tweet: oltre ai 140 caratteri del messaggio vero e proprio troviamo una sezione piuttosto vasta con le informazioni sull’autore e un’altra sulla sua localizzazione geografica.
Tali informazioni sono destinate ad aumentare ulteriormente, vista l’imminente implementazione delle cosiddette annotation. Come spiegato da Read/Write Web:

With annotations, third-party Twitter developers can add any additional metadata to a Twitter post. That’s right, any data. And a tweet can have more than one annotation attached to it. This extra data will initially start off small – Twitter developer Marcel Molina said it will “probably” be around 512 bytes. But over time, it will gradually grow larger as Twitter rolls out the feature and scales up in order to support it. The company hopes to have it end up “around 2K,” says Molina. How developers use that extra space is entirely up to them – there can be one giant piece of extra data attached to a tweet or a thousand tiny ones.
With annotations, Twitter could become a platform for sharing anything, not just 140 characters of text.