# List a tier's versions

`GET https://evohub.io/api/v1/catalog/tiers/{id}/versions`

Part of the [Catalog API](https://docs.evohub.io/catalog.md) reference · operationId `listTierVersions`.

Every version the tier had, newest first, with who changed it and
when.

Requires the `catalog:component:read` scope.

## Authorization

Any one of:

- `bearerKey`
- `headerKey`

Where:

- `bearerKey`: HTTP Bearer — An EvoHub API key (`evohub_…`) as a bearer token.
- `headerKey`: API key in the header `X-API-Key` — An EvoHub API key (`evohub_…`).

## Path parameters

- `id` (string, required, example `tir_1f3a5c7e9b2d4f6a8c0e1b3d5f7a9c2e`): The tier's ID.

## Responses

### 200 — The versions.

Content type: `application/json`

Type: `object`

- `data` (array of TierVersion)
  - `version` (integer)
  - `name` (string)
  - `description` (string)
  - `targets` (SLATargets)
    - `availability` (number, example `99.9`): A percentage above 0 and at most 100, up to 3 decimals.
    - `response` (object): Minutes to acknowledge, per On-Call severity (`critical`, `high`, `medium`, `low`, `info`), 1 to 525600.
      - Other keys: integer
    - `resolution` (object): Minutes to resolve, per severity.
      - Other keys: integer
    - `support_hours` (object)
      - `kind` (string, required, one of `24x7`, `business`)
      - `timezone` (string, example `Europe/Istanbul`)
      - `days` (array of integer): ISO weekdays, 1 is Monday.
      - `from` (string, example `09:00`)
      - `to` (string, example `18:00`)
    - `max_unowned_days` (integer, min 0, max 3650)
  - `changed_by` (string)
  - `changed_at` (string (date-time))

### 401 — No API key was sent, or it is unknown, revoked or expired (`UNAUTHORIZED`).

Content type: `application/json`

Type: `Error`

- `error` (object, required)
  - `code` (string, required, example `NOT_FOUND`)
  - `message` (string, required, example `not found`)
  - `request_id` (string)

### 403 — The key lacks a scope this endpoint needs (`FORBIDDEN`).

Content type: `application/json`

Type: `Error`

- `error` (object, required)
  - `code` (string, required, example `NOT_FOUND`)
  - `message` (string, required, example `not found`)
  - `request_id` (string)

### 404 — Nothing with this ID (or slug) exists in the organization (`NOT_FOUND`).

Content type: `application/json`

Type: `Error`

- `error` (object, required)
  - `code` (string, required, example `NOT_FOUND`)
  - `message` (string, required, example `not found`)
  - `request_id` (string)

### 429 — Too many requests (`RATE_LIMITED`). Wait for `Retry-After` seconds.

Headers:

- `Retry-After` (integer): Seconds to wait before retrying.

Content type: `application/json`

Type: `Error`

- `error` (object, required)
  - `code` (string, required, example `NOT_FOUND`)
  - `message` (string, required, example `not found`)
  - `request_id` (string)

### 500 — Something went wrong on EvoHub's side (`INTERNAL_ERROR`). Retry later.

Content type: `application/json`

Type: `Error`

- `error` (object, required)
  - `code` (string, required, example `NOT_FOUND`)
  - `message` (string, required, example `not found`)
  - `request_id` (string)

## Example request

```bash
curl -X GET 'https://evohub.io/api/v1/catalog/tiers/tir_1f3a5c7e9b2d4f6a8c0e1b3d5f7a9c2e/versions' \
  -H 'Authorization: Bearer <TOKEN>'
```