How to get your Resend API usage, balance and spend programmatically

What the Resend API exposes

Call it yourself

Credential. A full-access Resend API key (re_…), created under API keys. It can also send mail and manage domains, so make a dedicated one you can revoke.

curl https://api.resend.com/usage \
  -H "Authorization: Bearer $RESEND_API_KEY"

{
  "object": "usage",
  "emails": {
    "daily": { "used": 1, "limit": 100, "resets_at": "2026-10-21T23:59:59.999Z" },
    "monthly": { "used": 27, "limit": 3000, "resets_at": "2026-11-09T17:59:30.515Z" }
  },
  "contacts": { "used": 0, "limit": 1000 },
  "domains": { "used": 3, "limit": 3 }
}

Gotchas

• A sending-only key gets 401 restricted_api_key on /usage and /domains.
• A limit of null means no cap.
• The daily window resets at UTC midnight. The monthly window resets on your billing anniversary, not the calendar month.
• The response has no plan name, no dollar amounts and no account name, so Argus labels the connection team-wide.
• Every key on the team shares one rate limit of 10 requests per second.
• Past a quota the send API returns 429 daily_quota_exceeded or monthly_quota_exceeded.

How Resend charges

Transactional email by monthly volume (Free 3,000/mo and 100/day, Pro, Scale), with opt-in pay-as-you-go overage per 1,000 emails. Marketing contacts are a separate subscription.

Free allowance. 3,000 a month. Free plan: 100/day too. The daily window resets at UTC midnight.

At zero. Past the daily or monthly quota the API returns 429 daily_quota_exceeded or monthly_quota_exceeded. With pay-as-you-go overage on, paid plans keep sending until 5x the monthly quota, then pause until the next billing cycle.

• 10 requests per second, per team. Shared by every key on the team; the same on every plan. Higher limits on request.

Or let Argus track it

Paste the key once. Argus keeps the ledger, and your coding agent reads it through the MCP server.

• Tracks the plan: the allowance, what's used this period, the reset date, and when you cross into overage.
• With the SDK, counts each call and every 429 against the plan's allowance, since there's no meter to read.
• Emails you on low balance, days to zero, a spend spike, or projected overage.
• Hands all of it to your coding agent over MCP, so it can ask what a run cost or how much runway is left without leaving the editor.

> what has resend cost today, and how long until it runs out?

get_overview       → resend: mtd spend, burn per day, days to zero
get_request_costs  { "provider": "resend", "limit": 25 }
get_advisories     → credits_low, spend_spike, rate_limit_low …

Questions

Does Resend have an API for its balance?

Quota, not dollars. GET https://api.resend.com/usage returns used and limit for emails (daily and monthly, with reset times), contacts, segments, domains and automation runs. It needs a full-access key.

Can I get Resend spend per day from the API?

No. Count calls and price them yourself, or let the Argus SDK do it.

What happens when Resend credits run out?

Past the daily or monthly quota the API returns 429 daily_quota_exceeded or monthly_quota_exceeded. With pay-as-you-go overage on, paid plans keep sending until 5x the monthly quota, then pause until the next billing cycle.

What key does Argus need for Resend?

A full-access Resend API key (re_…), created under API keys. It can also send mail and manage domains, so make a dedicated one you can revoke.

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