One of the most common ways SEO agencies will rip off clients is with unnecessary schema implementation. Schema is code that makes you get special features in Google like this. With no schema.
With schema, you get a lot more clicks when you get the special feature in Google.
But Google has actually deprecated a lot of schema over the years, and agencies just ignore this. Now the new narrative is schema makes you get cited in LLMs. If you hear people say you need structured data to get mentioned in LLMs, they're usually talking about schema.
Ahrefs, one of the most reputable SEO software companies, just did this study. We tracked 1,885 pages adding schema. AI citation is barely moved.
Adding schema didn't boost citations on any platform. It had a negative effect on Google's AI overviews, statistically indistinguishable from 0 on Google AI mode, also statistically indistinguishable from 0 in ChatGPT.
This was a thorough study. You can see it for yourself here. Talk to your agency to make sure you're only focusing on schema that gives you special visible features in Google.
Aside from that, schema is a huge money suck to companies by SEO agencies, and you should be warned.