How to update an Assets Object field with the value of an attribute from another Assets field using

How to update an Assets Object field with the value of an attribute from another Assets field using Automation?

Hello everyone,

I'm working with Jira Service Management and trying to automatically update an Assets Object field based on an attribute from another Assets field using an automation rule.

I have two object types in my Assets schema:

• Products
• Services

Each Product has an attribute Service, which is a reference to an object in the Services schema.

In my JSM, I have two custom Assets Object fields:

1. "Product" → Allows users to select a product.
2. "Service" â†’ Should be automatically updated with the service linked to the selected product.

If a user selects "Jira Software" in the "Product" field, then the "Service (test)" field should automatically populate with "Atlassian Support".

I Have Tried:

1. Trigger: When the "Product" field is updated.
2. Create a variable serviceKey storing {{issue.Produit.Service.key}}.
3. Update the "Service (test)" field using the following JSON 

             { "fields": { "customfield_9999": [ { "key": "{{serviceKey}}" } ] } }

Whit this: 

• The automation runs without errors.
• The variable serviceKey is correctly retrieved (e.g., "SERV-64").
• But the "Service (test)" field is not updated.

Is the JSON format correct for updating an Assets Object field? Is there a better approach to dynamically retrieve and inject the "Service" attribute into the "Service (test)" field?

Thanks in advance for your help!