InboxTender API
Manage contacts, email, and SMS from CRMs, scripts, and agents.
The InboxTender API lets your other tools write straight into your workspace. Create or merge contacts, and manage email and SMS conversations through the messaging API.
Base URL https://api.inboxtender.comEvery request is authenticated with a workspace API key and every response body is JSON.
Using an AI agent? These docs are agent-readable: point it at
/llms.txt for the index or
/llms-full.txt for everything on
one page. Install the InboxTender skill
for the conversation-management workflow.
What it's for
- Push leads from anywhere — a website form, a marketplace scraper, a Zapier step, your existing CRM's automation.
- Safe to re-send —
POST /api/v1/contactsmerges by phone or email instead of duplicating, and it never overwrites a name or note your team wrote. - The assistant picks them up — pushed contacts appear on the Contacts screen with their tags, ready for broadcasts and follow-ups.
Errors
Errors always share one shape:
{ "error": { "code": "unauthorized", "message": "That API key is unknown or revoked." } }| Status | Code | Meaning |
|---|---|---|
| 400 | invalid_json, invalid_body, invalid_query | The request doesn't parse or validate. |
| 401 | unauthorized | Missing, unknown, or revoked API key. |
| 403 | plan_required | The workspace's plan doesn't include the API. |
| 404 | not_found | Unknown endpoint or contact id. |
| 422 | invalid_identifier | Neither phone nor email is a usable address. |
| 429 | rate_limited | Over the request budget — honor Retry-After. |