Compared to vCard, MeCard format only stores one single contact, a few labels, and a few data pieces to be set in a typical phonebook.
There is no place on the web that defines a standard for MeCard. It is not described by the ISO, nor is there an RFC for it. As of 2016, the page at NTT DoCoMo that originally defined the layout returns 404, and searching their web site for "MeCard" turns up only a few unrelated references.
MeCard format starts with the tag MECARD and it finishes with two semicolons (;;)
The supported tags include:
Note on the ADR: field: Although the original NTT DoCoMo page described the format as shown, in practice almost no QRCode apps that recognize MeCards decompose the address as a set of comma separated fields. They instead display the contents of the field directly. This indicates that, in practice, the field should be formatted according to local layout conventions.