---
title: "Changes to Add a custom variable to an existing model"
method: POST
path: "/models/{model_id}/custom-variables"
---

# Changes to Add a custom variable to an existing model

`POST /models/{model_id}/custom-variables`

> Every recorded change to this operation, newest first.

## Timeline

Changed in 2 of 25 revisions.

- **2026-10-20** `4185f624bbb8`: 2 breaking, 2 info
- **2026-09-30** `ea3d377fec1a`: 1 breaking

## Changes

- **2026-10-20** `4185f624bbb8`: 2 breaking, 2 info
  - the response property `user_id` became optional for the status `201`
  - response property `user_id` list-of-types was widened by adding types `null` to media type `application/json` of response `201`
  - added the optional property `project_id` to the response with the `201` status
  - added the optional property `source_model_id` to the response with the `201` status
- **2026-09-30** `ea3d377fec1a`: 1 breaking
  - for the `path` request parameter `model_id`, the format changed from no format to `uuid`

---

[Operation](https://skmtc.dev/ionworks/apis/ionworks-api/docs/models/:model_id/custom-variables/post.md) - [API](https://skmtc.dev/ionworks/apis/ionworks-api.md) - [Page](https://skmtc.dev/ionworks/apis/ionworks-api/changes/models/:model_id/custom-variables/post)