If you're wondering whether api.a.mts.ru is a scam or safe to use, the short answer is that it's likely a legitimate technical endpoint belonging to MTS, one of Russia's largest telecom providers. The domain itself returns a 404 page, meaning there's no public website here — it's probably an API or internal service that isn't meant for casual browsing.
For a subdomain of a major company, you'd expect proper SSL and clean reputation scores, and this one delivers both. Nothing in the signal data suggests phishing, malware, or blacklisting. The lack of contact information, privacy policy, or social media presence is completely normal for a backend endpoint. If you were sent to this URL as part of a service or app from MTS, it's likely legitimate. Just don't expect to find a user-friendly site — there's nothing to interact with.