Plan limits and the 402 plan_required errorPlans and limits

A write that needs a feature your team's plan doesn't include gets a 402 with "code": "plan_required". The body names the feature and the cheapest plan that has it, so your client can offer the upgrade without its own copy of the plan table.

{  "code": "plan_required",  "message": "Escalation policies need the Team plan.",  "requestId": "01J9F3Q0YB4V7XZ2M8K6R5T1AC",  "requiredFeature": "escalationPolicies",  "requiredPlan": "team"}

Reads and deletes are never gated, so a team that downgrades can still see and tidy everything. A downgrade deletes nothing. Anything the new plan doesn't include is paused, stays visible, and resumes when the plan comes back.

A message is one send, however many devices it reaches. The free plan includes 10,000 a month. Past the allowance, sends get a 429 naming the reset date. You're never billed for overage.