Quickstart: Python

One dependency (pip install requests) and nine lines.

send.py

import requests, uuid

res = requests.post(
    "https://api.calder.click/v1/emails",
    headers={
        "Authorization": "Bearer calder_sk_test_…",
        "Idempotency-Key": str(uuid.uuid4()),
    },
    json={
        "from": "app@acme.com",
        "to": "you@example.com",
        "subject": "Hello from Calder",
        "text": "It works.",
    },
    timeout=10,
)
print(res.json()) # {"id": "em_9f2k41xq", …}

Always set a timeout. The API answers in milliseconds, but your HTTP client should never wait forever — on timeout, retry with the same idempotency key.

Next: why that key matters, then Webhooks.