Are there any guidelines for sending and receiving attachments on the Official WhatsApp API?

Media → Supported Content Types → File Extensions → Size Restriction

Document → PDF and Office documents → .pdf, .do*, .xl, .ppt, .sx*, .od* → 100 MB

Image → image/jpeg, image/png → .jpeg, .jpg, *.png → 5 MB

Audio → audio/acc, audio/mp4, audio/amr, audio/mpeg, audio/ogg; codecs=opus

.acc, .mp4, .mp4a, .amr, .mpeg, .ogg → 16 MB

Video → video/mp4, video/3gpp → .mp4, .3gp, *.3g2 → 16MB