You should decide to work with a developer to implement structured data on a page when there are a large number of required or recommended properties in a markup.
- When there are multiple schema markups that you want to implement on a single page
- When you are unable to use a plugin to add structured data to your website
- You should always work with a developer to implement structured data.
- When there are a large number of required or recommended properties in a markup
The correct answer is: When there are a large number of required or recommended properties in a markup
Structured data implementation involves dealing with code, making it a task usually handled by developers. While some simpler Schema markups can be managed without a developer, more complex markups with numerous required or recommended properties would benefit from a developer’s expertise. The complexity increases with the number of properties, and having a developer ensures that the structured data is implemented correctly, maximizing the benefits for SEO and rich results in search engines.
Source: HubSpot Lesson: Optimizing Your Website for Rich Results