> For the complete documentation index, see [llms.txt](https://docs.fulfillmenttools.com/documentation/llms.txt). Markdown versions of documentation pages are available by appending `.md` to page URLs; this page is available as [Markdown](https://docs.fulfillmenttools.com/documentation/getting-started/custom-attributes.md).
# Custom attributes
The `customAttributes` field can be added to certain fulfillmenttools entities. These attributes contain information relevant to connectors or services outside of fulfillmenttools.
Example use cases for `customAttributes` include storing a consumer rating from a shop or a foreign key that relates to data in a connected system. The `customAttributes` are stored and can be retrieved through the various fulfillmenttools APIs.
{% hint style="info" %}
The `customAttributes` field shouldn't be confused with the `attributes` field mentioned in [customization via article attributes](/documentation/by-pillar/global-inventory-hub/articles/article-attributes.md).
{% endhint %}
### Custom attribute inheritance
Custom attributes are inherited during the creation of entities within fulfillmenttools. For example, when `customAttributes` are supplied for order line items, the resulting pick job line items also contain these `customAttributes`. In general, all subsequent entities inherit these attributes.
{% hint style="danger" %}
**Limitations**
Each `customAttributes` object is subject to a size limit of 15,360 characters, as the entire object is serialized into a string. The API returns an HTTP 400 error if an entity creation or update exceeds this limit. Additionally, keys within a `customAttributes` object must not start with a `$` character and must not contain a `.` character.
{% endhint %}
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