It was harder than I thought to find a good information (for free) about the NFC protocol standards. After reading countless application notes, datasheets, forums and what-not, I came up with the first workable software. I wrote a tiny standalone NFC library which supports generation of NFC Text and URI types of messages. Checkout on github: https://github.com/beast-devices/BeastCard

Useful info about NFC can be found here:

http://sweet.ua.pt/andre.zuquete/Aulas/IRFID/11-12/index-docs.html

https://www.nxp.com/docs/en/data-sheet/NTAG213_215_216.pdf

https://learn.adafruit.com/adafruit-pn532-rfid-nfc/ndef

https://stackoverflow.com/questions/22357664/android-nfc-smart-poster-ndef-record-with-concatenated-uri-and-text-content

https://www.netes.com.tr/netes/dosyalar/dosya/B6159F60458582512B16EF1263ADE707.pdf

https://flomio.com/2012/05/ndef-basics/

https://stackoverflow.com/questions/14669193/format-for-data-on-nfc-business-cards