Web chat
Richest surface. Cards, carousels, file upload
Users expect a visible human-handoff button
Mobile in-app
Authenticated session, so the assistant knows who it is talking to
Screen real estate; keep answers short and
actionable
WhatsApp Business
Template-message rules and 24-hour session windows
Business-initiated messages need pre-approved
templates
Apple Messages for Business
Native list pickers, Apple Pay
Brand registration and Apple's review process add
lead time
RCS
Rich cards on Android without an app install
Carrier and device support still uneven
SMS
Universal reach, no rich formatting
160-character discipline, and TCPA consent for
outbound
Facebook Messenger
Consumer-familiar, good for retail
Meta policy windows on proactive messaging
Slack / Microsoft Teams
Internal assistants where employees already work
Role-based access control matters more than tone
Voice and IVR
No visual fallback, so recovery has to be conversational
Latency budget under roughly one second, plus
barge-in handling
Email
Asynchronous, long-form, tolerant of slower responses
Threading and quoting break naive context windows
Agent desktop (assist mode)
The assistant drafts, a human sends
Highest-trust starting point, and the fastest path
to a measurable win