> ## Documentation Index
> Fetch the complete documentation index at: https://openphone-dev.mintlify.site/llms.txt
> Use this file to discover all available pages before exploring further.
# Introduction
> What the Quo API covers, the conventions it follows, and where to start.
Quo is the phone system your business answers with: one shared place for every call, text, and the customer behind them. The Quo API opens that system to the rest of your software. Your CRM can pull conversation history and a script can keep contacts in sync. So can an AI agent, at 2am, without waking anyone up.
You don't need to be a developer to get value from this page. You need to know what the API can reach, what it promises, and where to start.
## One request, end to end
Here is the whole shape of the API in a single exchange: an API key in the `Authorization` header, a date in the `Quo-Api-Version` header, JSON back.
```bash theme={null}
curl https://api.quo.com/users?limit=1 \
--header "Authorization: YOUR_API_KEY" \
--header "Quo-Api-Version: 2026-03-30"
```
```json theme={null}
{
"data": [
{
"id": "USu3X8sIB9",
"email": "renee@pinkswindows.com",
"firstName": "Renee",
"lastName": "Ortiz",
"pictureUrl": null,
"role": "owner",
"createdAt": "2024-08-02T17:31:08Z",
"updatedAt": "2026-05-19T09:12:45Z"
}
],
"nextCursor": null
}
```
Every endpoint follows this pattern. If you can read this response, you can read all of them.
## The API at a glance
| | |
| -------------- | -------------------------------------------------------------------------------------------------------------------------- |
| Base URL | `https://api.quo.com` |
| Authentication | API key in the `Authorization` header. [Details](/2026-03-30/authentication) |
| Versioning | `Quo-Api-Version: 2026-03-30` header, required on every request. [How versioning works](/2026-03-30/versioning) |
| Format | JSON in, JSON out. Single resources arrive wrapped in `data`; lists add `nextCursor`. |
| Pagination | Cursor-based: `limit` (1–50, default 10) and `after`. [Making requests](/2026-03-30/requests) |
| Rate limit | 10 requests per second per API key. [Rate limits](/2026-03-30/rate-limits) |
| Errors | A structured envelope that names the field at fault and can include a `trace` id for support. [Errors](/2026-03-30/errors) |
## How it's designed
Three rules shape everything here.
**Versions never change after they ship.** New endpoints and new optional fields land inside the current version. Anything that would break existing integrations gets a new dated version, and you upgrade when you choose to. The full contract fits on [one page](/2026-03-30/versioning).
**Errors name the field at fault.** Every error tells you what went wrong and points to the offending field. When a response includes a `trace` id, support can use it to find your exact request in our logs.
**The docs serve people and machines.** These pages, the OpenAPI spec, and the [LLM-ready formats](/2026-03-30/ai-agents) describe one contract. An agent and a human reading them reach the same understanding.
## What's available today
This version is new, and we'd rather show you a precise map than a generous one.
| Surface | Status |
| ------------------------------ | -------------------------------------------------------------------------------------------------------------------- |
| Users | **Available.** List and retrieve workspace users. |
| Calls, transcripts & summaries | In development |
| Contacts | In development |
| Conversations & messages | **In progress.** Mark a conversation as read and retry a failed message are live; more endpoints are in development. |
| Phone numbers | In development |
New endpoints are announced in the [changelog](/2026-03-30/changelog) as they land (there's an RSS feed). Additions never break the version you're on, so picking them up is optional.
Need messaging, calls, or contacts today? The [v1 API](/mdx/api-reference/introduction) remains fully supported. Switch versions with the selector in the top navigation; new capability ships here.
## Where to next
From API key to a `200` in about two minutes.
What a dated version guarantees, and why it's in a header.
Headers, envelopes, ids, timestamps, and pagination.
MCP, llms.txt, and the spec. Quo for software that reads.