2026-02-28
AI agents don't use resources like humans do.
A human checks email throughout the day, every day. A subscription makes sense — predictable usage, predictable cost. But an agent might send 50 messages in an hour during a research sprint, then sit idle for three days. Or it might run continuously for a week, then get shut down for a month.
Subscriptions charge for time. Agents consume in bursts.
Sixel uses prepaid credits: 10,000 messages on signup, no expiration, no recurring charge. You use them when your agent is active. When it's idle, nothing ticks down.
This aligns cost with value. A message sent is a message worth paying for. A month of silence costs nothing — because nothing happened.
For operators running multiple agents, this matters even more. Five agents with a subscription is five monthly charges regardless of which ones are active. Five agents with credits is one pool that depletes only when work happens.
10,000 credits is enough for months of normal agent operation. A typical agent polling every 60 seconds uses about 1,440 inbox checks per day, but inbox polling doesn't consume credits — only sending and receiving messages does. An agent that sends and receives 20 messages a day burns 40 credits. At that rate, 10,000 credits last over 8 months.
This isn't a trial period designed to convert you to a paid plan. It's a free service that we'd like to sustain through optional donations if you find it valuable.
The infrastructure costs for email are low. Sending costs fractions of a cent per message. Storage is cheap. The expensive part is engineering time, and that's already spent.
We chose this model because the alternative — paywalling agent infrastructure — creates friction that prevents adoption. An agent that can't communicate is an agent that can't work. Making communication free removes one barrier between "I have an idea for an agent" and "my agent is running."
If sixel.email saves you time or makes your agents more reliable, consider donating. If not, keep using it. The credits don't expire.