Stripped down version of the PetStore example in OpenAPI v3.0.1

swagger.json

{
  "openapi": "3.0.1",
  "info": {
    "description": "This is a sample server Petstore server.  You can find out more about Swagger at [http://swagger.io](http://swagger.io) or on [irc.freenode.net, #swagger](http://swagger.io/irc/).  For this sample, you can use the api key `special-key` to test the authorization filters.",
    "version": "2.0.0",
    "title": "Swagger Petstore",
    "termsOfService": "http://swagger.io/terms/",
    "contact": {
      "email": "apiteam@swagger.io"
    },
    "license": {
      "name": "Apache 2.0",
      "url": "http://www.apache.org/licenses/LICENSE-2.0.html"
    }
  },
  "servers": [
    {
      "url": "https://petstore.swagger.io/v2"
    }
  ],
  "tags": [
    {
      "name": "pet",
      "description": "Everything about your Pets",
      "externalDocs": {
        "description": "Find out more",
        "url": "http://swagger.io"
      }
    }
  ],
  "paths": {
    "/pet/{petId}": {
      "get": {
        "tags": [
          "pet"
        ],
        "summary": "Find pet by ID",
        "description": "Returns a single pet",
        "operationId": "getPetById",
        "produces": [
          "application/json",
          "application/xml"
        ],
        "parameters": [
          {
            "name": "petId",
            "in": "path",
            "description": "ID of pet to return",
            "schema": {
              "type": "integer",
              "format": "int64"
            }
          }
        ],
        "responses": {
          "200": {
            "description": "successful operation",
            "schema": {
              "$ref": "#/components/schemas/Pet"
            }
          },
          "400": {
            "description": "Invalid ID supplied"
          },
          "404": {
            "description": "Pet not found"
          }
        },
        "security": [
          {
            "api_key": []
          }
        ]
      }
    }
  },
  "components": {
    "schemas": {
      "Category": {
        "type": "object",
        "properties": {
          "id": {
            "type": "integer",
            "format": "int64"
          },
          "name": {
            "type": "string"
          }
        },
        "xml": {
          "name": "Category"
        }
      },
      "Pet": {
        "type": "object",
        "required": [
          "name",
          "photoUrls"
        ],
        "properties": {
          "id": {
            "type": "integer",
            "format": "int64"
          },
          "category": {
            "$ref": "#/components/schemas/Category"
          },
          "name": {
            "type": "string",
            "example": "doggie"
          },
          "photoUrls": {
            "type": "array",
            "xml": {
              "wrapped": true
            },
            "items": {
              "type": "string",
              "xml": {
                "name": "photoUrl"
              }
            }
          },
          "tags": {
            "type": "array",
            "xml": {
              "wrapped": true
            },
            "items": {
              "xml": {
                "name": "tag"
              },
              "$ref": "#/components/schemas/Tag"
            }
          },
          "status": {
            "type": "string",
            "description": "pet status in the store",
            "enum": [
              "available",
              "pending",
              "sold"
            ]
          }
        },
        "xml": {
          "name": "Pet"
        }
      },
      "Tag": {
        "type": "object",
        "properties": {
          "id": {
            "type": "integer",
            "format": "int64"
          },
          "name": {
            "type": "string"
          }
        },
        "xml": {
          "name": "Tag"
        }
      }
    },
    "securitySchemes": {
      "api_key": {
        "type": "apiKey",
        "name": "api_key",
        "in": "header"
      }
    }
  }
}