TL;DR The Swagger Petstore is useful for demonstrating OpenAPI, but it is a poor REST design reference. It mixes singular and plural resource names, puts action verbs in URLs, uses incorrect HTTP status codes, exposes passwords in GET requests, returns bare arrays, and uses non-standard errors. ...
Source: [Dev.to](https://dev.to/preecha/why-is-the-swagger-petstore-example-a-bad-rest-api-design-dei)