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

# APP_DATA_KEY_NOT_DECLARED

> HTTP 400, from PUT /data/{ownerType}/{ownerId}/{key}.

Its problem `type`: `https://developers.tassyir.io/errors/app-data-key-not-declared`.

## What to do

HTTP 400. Your installation's version does not declare that key for that owner
type. Declare it under `[[data.definitions]]`, upload, and have the merchant
accept the update.

## Answered by

HTTP 400, from:

* [`PUT /data/{ownerType}/{ownerId}/{key}`](/api-reference/admin/data/write-a-value)

The shape of every problem, and how `@tassyir/app` reports it: [Errors](/guides/errors).


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