> ## Documentation Index
> Fetch the complete documentation index at: https://docs.powerdialer.ai/llms.txt
> Use this file to discover all available pages before exploring further.

# Best practices

> How to integrate reliably: batching, ids, phone formats and key handling.

* **Send one batch of up to 10,000 contacts** rather than one request per contact. A batch is atomic, so retry the whole batch on a `500`.
* **Store the list `id`** from the create response; names are not unique.
* **Use E.164 phone numbers** (`+1...`). They avoid duplicate contacts and make removal by number reliable.
* **Adding is append-only.** To change a contact's details, remove it by phone number and add it again.
* **Pass the user's timezone** to the analytics call so day boundaries match their reports.
* **Keep the API key on your server only.** Ask PowerDialer to rotate it if it is ever exposed; two keys can be valid during a rotation.
* **Choose the user header deliberately.** `x-user-id` is stable across email changes; `x-user-email` is easier to configure. If both are sent, `x-user-id` wins.


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