What would you say about an API where all methods are implemented via POST (no GET, PUT, PATCH, DELETE)?

Using only POST for all API methods is a violation of REST principles and HTTP standards. In REST, each HTTP method has its semantic meaning:

• GET — retrieving data (without side effects)
• POST — creating resources or performing actions
• PUT/PATCH — updating resources
• DELETE — deleting resources

If all methods are implemented via POST, it leads to:

• Loss of semantics and clarity of the API
• Caching issues (GET requests are usually cached, POST — not)
• Difficulties with debugging and integration
• Violation of idempotency (GET, PUT, DELETE are usually idempotent, POST — not)

This approach may be justified in some cases (for example, client restrictions, proxies, or firewalls), but overall it is a bad practice. It is better to use methods as intended for convenience, performance, and compliance with standards.