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

# Create cohort

> Creates a named patient cohort in your organization.

```python theme={null}
olira.create_cohort(name: str, description: str | None = None) -> Cohort
```

**Requires scope:** `api:manage-patients`

Cohorts start empty — use add\_patients\_to\_cohort to enroll patients. Names must be unique per organization.

## Parameters

<ParamField body="name" type="str" required>
  Display name; unique per organization (1–200 characters).
</ParamField>

<ParamField body="description" type="str | None">
  Optional free-text description.
</ParamField>

## Returns

`Cohort` — Created cohort with Olira-assigned id.

<ResponseField name="id" type="str">
  Olira cohort id.
</ResponseField>

<ResponseField name="name" type="str">
  Display name.
</ResponseField>

<ResponseField name="description" type="str | None">
  Optional description.
</ResponseField>

<ResponseField name="patient_ids" type="list[str]">
  Patient ids in this cohort.
</ResponseField>

<ResponseField name="created_at" type="str | None">
  ISO 8601 creation timestamp.
</ResponseField>

<ResponseField name="updated_at" type="str | None">
  ISO 8601 last-updated timestamp.
</ResponseField>

## Raises

| Exception         | When                                                                                                                  |
| ----------------- | --------------------------------------------------------------------------------------------------------------------- |
| `AuthError`       | HTTP 401 or 403 — invalid API key or insufficient OAuth scope for this endpoint.                                      |
| `ValidationError` | HTTP 400, 404, or 422 — malformed JSON, unknown patient, or validation failure (message includes response excerpt).   |
| `ServerError`     | HTTP 409 (e.g. conflicting external identifier) or repeated 5xx after retries; includes status\_code when applicable. |
| `RateLimitError`  | HTTP 429 — rate limited; check retry\_after (seconds).                                                                |
| `NetworkError`    | Connection timeout, DNS failure, or read error after retries.                                                         |

<RequestExample>
  ```python Python theme={null}
  import olira

  olira.init(api_key="YOUR_API_KEY")
  cohort = olira.create_cohort(name="High-Risk Patients", description="Patients flagged for weekly review")
  print(cohort.id)
  ```

  ```http HTTP theme={null}
  POST /v1/cohorts
  Authorization: Bearer YOUR_API_KEY
  Content-Type: application/json

  {
    "name": "High-Risk Patients",
    "description": "Patients flagged for weekly review"
  }
  ```
</RequestExample>

<ResponseExample>
  ```python 200 theme={null}
  Cohort(
      id="68582e4a0a0b3c1234567890",
      name="High-Risk Patients",
      description="Patients flagged for weekly review",
      patient_ids=[],
      created_at="2026-06-25T10:00:00Z",
      updated_at="2026-06-25T10:00:00Z",
  )
  ```

  ```json 401 theme={null}
  {
    "error": true,
    "status_code": 401,
    "error_type": "authentication_error",
    "message": "Could not validate credentials",
    "details": [
      {
        "type": "authentication_error",
        "message": "Could not validate credentials"
      }
    ],
    "timestamp": "2026-05-06T12:00:00+00:00"
  }
  ```

  ```json 403 theme={null}
  {
    "error": true,
    "status_code": 403,
    "error_type": "authorization_error",
    "message": "Insufficient OAuth scope for this endpoint",
    "details": [
      {
        "type": "authorization_error",
        "message": "Insufficient OAuth scope for this endpoint"
      }
    ],
    "timestamp": "2026-05-06T12:00:00+00:00"
  }
  ```

  ```json 404 theme={null}
  {
    "error": true,
    "status_code": 404,
    "error_type": "not_found_error",
    "message": "Patient not found",
    "details": [
      {
        "type": "not_found_error",
        "message": "Patient not found"
      }
    ],
    "timestamp": "2026-05-06T12:00:00+00:00"
  }
  ```

  ```json 422 theme={null}
  {
    "error": true,
    "status_code": 422,
    "error_type": "validation_error",
    "message": "Request validation failed (1 error)",
    "details": [
      {
        "type": "missing",
        "message": "Field required",
        "field": "patient_id",
        "location": ["body", "patient_id"],
        "input_value": null
      }
    ],
    "timestamp": "2026-05-06T12:00:00+00:00"
  }
  ```

  ```json 429 theme={null}
  {
    "error": true,
    "status_code": 429,
    "error_type": "server_error",
    "message": "Rate limit exceeded",
    "details": [
      {
        "type": "rate_limit",
        "message": "Too many requests; retry after backoff"
      }
    ],
    "timestamp": "2026-05-06T12:00:00+00:00"
  }
  ```

  ```json 500 theme={null}
  {
    "error": true,
    "status_code": 500,
    "error_type": "internal_server_error",
    "message": "An internal server error occurred",
    "details": [
      {
        "type": "internal_server_error",
        "message": "An unexpected error occurred while processing your request"
      }
    ],
    "timestamp": "2026-05-06T12:00:00+00:00"
  }
  ```
</ResponseExample>