# API overview & authentication

## What the CTD API lets you build

The CTD API lets you embed relationship data — who you know, how well, warm paths, job changes — directly into your CRM, internal dashboard, data warehouse, or any tool your team already lives in. No need to switch tabs. No manual exports.

## The three API tiers

| API | Who it's for | Plans | Documentation |
| --- | --- | --- | --- |
| User API — Freemium | Individual users | Free, Team, Business | [View docs](https://app.ctd.ai/account/api-access/documentation) |
| User API — Team & Business | Individual users on paid plans | Team, Business | [View docs](https://app.ctd.ai/account/api-access/documentation?type=user) |
| Workspace API | Admins, system integrations | Team, Business | [View docs](https://app.ctd.ai/account/api-access/documentation?type=workspace) |

**Note:** Team and Business users have access to both the Freemium and Team & Business endpoints.

## Getting your API key

Go to [app.ctd.ai/account/api-access/api-keys](https://app.ctd.ai/account/api-access/api-keys), create a key, and copy it. Keep it secret — it grants access to your network data.

## Authentication

Every request requires two headers:

```
ctd-api-key: YOUR_API_KEY
ctd-client-id: you@yourcompany.com
```

`ctd-client-id` is your organization email address — used for audit logging and access control.

Example:

GET`/user/contacts-api/people/details`

Returns details for a contact identified by email or LinkedIn URL.

```
curl "http://api.ctd.ai/user/contacts-api/people/details?email=john@example.com" \
  -H "ctd-api-key: YOUR_API_KEY" \
  -H "ctd-client-id: you@yourcompany.com"
```

## Response codes

- **200** — Success
- **400** — Bad request (check your parameters)
- **403** — Forbidden (wrong key, or endpoint requires a higher tier)
- **404** — Not found
- **500** — Server error

Have a question or running into an issue? Email us at [support@ctd.ai](mailto:support@ctd.ai) — we're happy to help.