The first step in credit-first AI billing is deciding what to charge for. Billable events are the bridge between what your product does and what users pay for. Get them right, and billing feels natural. Get them wrong, and you're either undercharging, overcharging, or confusing everyone.
A billable event should map to a moment of value the user recognizes. A chat reply, an image generation, a document summary, an agent run — these are the actions users take and understand. They are not input tokens, output tokens, or model-specific API calls.
The rule
One event = one user-facing action. If the user wouldn't describe it that way, reconsider.
Event granularity
Too coarse, and you can't price fairly. Too fine, and you create complexity nobody needs. Most AI products land on a small set of event types: chat, image, summary, agent step. Each maps to a credit cost. Keep the set small and stable.
Naming and structure
Use clear, product-native names: chat.reply, image.generate, summary.create. Avoid provider jargon. Your billing system will meter these; your users will see them in usage history. Names matter for trust and clarity.
If you're building an AI product and want a cleaner way to charge for usage than raw tokens or hand-built billing logic, Chargly is built for exactly that.