Spending caps for AI agents

A Tillpad key cannot keep spending after the account cap or that key's own operation budget. The call comes back 402 or 429 with the budget still in the body. For developers who need a hard cap on agent spend. Pro is $9 a month.

Two ways Pro is capped

Human Pro is $9 per month and renews through Stripe. Each month includes 10,000 key-value operations, 100 MB storage, 5,000 index units, 2,000 searches, 500 inbound emails, and 5,000 outbound HTTP attempts. Past that, human Pro reports overage to Stripe until usage reaches 10 times the included amount. The next call returns 429.

Agent prepaid Pro is $9 for 30 days or $24 for 90 days. It uses the same included monthly numbers and does not bill overage. The hard cap multiplier for a prepaid account is 1, so the included amount is the cap. Top-ups add 10,000 key-value operations for $1, or 1 GB of storage ceiling for $0.05. There is no top-up for search, indexing, inbound email, or outbound HTTP. Without a plan, metered calls are blocked.

Published unit prices on GET /api/config, for the meters that response includes, are $0.0001 per extra key-value operation, $0.05 per extra GB, $0.0005 per extra index unit, and $0.001 per extra search.

Check before a large call

GET /api/budget returns remaining included quota, hard caps, and checkout URLs. POST /api/budget/estimate with kind and amount says whether that future spend would be a 402 or a 429. kind is one of kvp_ops, storage_bytes, rag_index, rag_query, inbound_email, or outbound_http. For rag_index you can pass textLength or byteLength instead of amount.

MCP get_usage view=budget and estimate_usage are the same reads. They do not spend quota. manage_billing action=machine_pay returns the SKU and the URL the agent must POST. That call does not charge.

A key can also set opBudget, a maximum number of metered operations for that key. Omit it, or set 0, for no per-key cap. The account cap still applies.

curl -s -H "Authorization: Bearer tp_…" "https://tillpad.dev/api/budget"

curl -s -X POST "https://tillpad.dev/api/budget/estimate" \
  -H "Authorization: Bearer tp_…" \
  -H "Content-Type: application/json" \
  -d '{"kind":"rag_index","textLength":5000}'

Questions people ask

Will an agent on prepaid Pro run up an overage bill?

No. Prepaid agent Pro does not bill Stripe overage. Calls stop at the included quota, plus any key-value or storage top-up applied that month.

What does the client receive at the cap?

HTTP 402 when there is no active plan, or HTTP 429 when a hard cap is hit. The JSON includes code, actions, and budget. actions can point a human at Checkout or an agent at machine-pay.