MB-230 Extend Customer Service Practice Question
A Customer Service manager wants a custom button on the Case form that, when clicked, calls an external REST API to retrieve a customer's outstanding balance and displays it in a notification. The button must be available in both the web app and the Customer Service workspace, and no full-page reload should occur. The organization uses the Unified Interface only. Which approach should you recommend?
⚠ Common exam trap
The trap here is assuming that any JavaScript on the form can run on a button click, when only command bar customizations define clickable commands that execute script.
Answer choices
Why each option matters
Answer the question above first, then reveal the full breakdown to understand why each option is right or wrong.
Correct answer & explanation
✓
Create a ribbon workbench customization that adds a button to the Case form's command bar and associates a JavaScript web resource with the button's command.
A command bar button customized with a JavaScript web resource is the supported way to add a clickable action to a Unified Interface form that can call an external API and show a notification. It works in both the web client and Customer Service workspace without a page reload. OnLoad scripts, business rules, and embedded flows do not provide the required button-triggered behavior.
Answer analysis
Option-by-option breakdown
For each option: why learners choose it and why it is or isn't the right answer here.
- ✗
Add a JavaScript web resource to the Case form's OnLoad event that uses XMLHttpRequest to call the API.
Why it's wrong here
OnLoad runs when the form loads, not when a button is clicked, so the API call would fire immediately rather than on demand. It also cannot create a custom command button. While XMLHttpRequest can call REST APIs, placing the logic in OnLoad does not satisfy the requirement of a user-initiated button action, and no notification with the returned balance would be displayed on click.
- ✓
Create a ribbon workbench customization that adds a button to the Case form's command bar and associates a JavaScript web resource with the button's command.
Why this is correct
Command bar (ribbon) customizations let you add a button to the Case form that runs a JavaScript function on click. The script can call the external REST API and use the form's notification API to display the balance. This works in both the web app and Customer Service workspace because both use the Unified Interface ribbon, and no page reload occurs.
- ✗
Configure a business rule on the Case entity that calls the external API when the form is saved.
Why it's wrong here
Business rules cannot call external APIs; they only perform client-side actions on form fields. They are also triggered by field changes or save, not by a custom button click. This option does not provide a clickable button, cannot make external calls, and would not display a notification with the retrieved balance, so it fails the scenario's requirements.
- ✗
Create a Power Automate cloud flow triggered by a button and embed it using an IFRAME on the Case form.
Why it's wrong here
Power Automate button flows cannot be embedded as an IFRAME control on a form, and IFRAMEs are not supported in the Customer Service workspace. While a flow could call the API, displaying the result in a notification would require additional scripting. This approach does not meet the requirement of a custom button on the form with an immediate notification.
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JA
Written and reviewed by Johnson Ajibi, MSc IT Security
Senior Network & Security Engineer · founder of Courseiva
Last reviewed September 2026 · checked against the official Microsoft exam blueprint
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