API Standardization

SwaggerHub CLI provides the api:validate command to scan a specific API version:

swaggerhub api:validate OWNER/API_NAME/VERSION  - validate a specific version

swaggerhub api:validate OWNER/API_NAME  - validate the default version

The output is a list of standardization errors and warnings with line numbers:

line    severity        description

2:      CRITICAL        'info.license.name' required -> API license must be present and non-empty string
2:      CRITICAL        'info.license.url' required -> API license must be present and non-empty string
4:      WARNING      Semantic Versioning-Version must be MAJOR.MINOR.PATCH
15:     CRITICAL        'delete a user' does not comply with the rule -> Summary should start with upper case and end with a dot

The exit codes are:

You can get the error list by sending a GET request to https://api.swaggerhub.com/apis/OWNER/API_NAME/VERSION/standardization in SwaggerHub SaaS or http(s)://SERVER/v1/apis/OWNER/API_NAME/VERSION/standardization in SwaggerHub On-Premise 1.26 and later. For example:

curl -H "Authorization: YOUR_API_KEY" https://api.swaggerhub.com/apis/MyOrg/MyApi/1.0.0/standardization

Sample response:

{
  "standardization": [
    {
      "line": 2,
      "description": "'info.license.url' required -> API license must be present and non-empty string",
      "severity": "CRITICAL"
    },
    {
      "line": 4,
      "description": "Semantic Versioning-Version must be MAJOR.MINOR.PATCH",
      "severity": "WARNING"
    },
    ...
  ]
}

View API documentation

Each operation must have an operationId. Code generators use operationId as method names, so use IDs that would be appropriate as method names. For example, GET /pets/{id} could have operationId: getPetById. API documentation also uses operationId to generate permalinks to individual operations.

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Operation summary is a short explanation of what the operation does. Summaries are displayed next to the operation paths in the API docs, and are also used by code generators to produce the method documentation. A summary is an analog of the /** ... */ comments in Java or the <summary> element in C# XML comments.

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Use this rule to ensure that the operation summaries are proper sentences.

# Good
summary: Upload user profile image.

# Bad
summary: upload user profile image

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Use the description element to explain what this operation does and document any prerequisites and usage specifics. The description can be multiline and use Markdown for rich text representation. Detailed, up-to-date documentation helps developers use your API more effectively.

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Tags are used to group operations logically into categories, such as Account, Payments, Reports, Search, and so on. Use the tags element to specify an array of tags for an operation.

SwaggerHub uses tags in a few ways:

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Some code generators use tags to group operations into the same API class file. Using a single tag per operation ensures that the operations will not duplicate across several class files.

# Good
paths:
  /pet:
    post:
      summary: Add a new pet to the store.
      tags:
      - pet     # <-----

# Bad
paths:
  /pet:
    post:
      summary: Add a new pet to the store.
      tags:
      - pet       # <-----
      - store     # <-----

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Successful and error responses are an important part of an API definition. A successful response has an HTTP status code in the 2xx range, such as 200 OK or 201 Created. Each operation must have at least one successful response defined. In OpenAPI 3.0 definitions, the '2XX' keyword can be used to represent all successful responses.

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The default response covers possible HTTP response codes that are not defined individually for an operation. It is usually used to represent error responses without listing various 4xx codes individually. That said, it is a good idea to explicitly define any known errors, such as 401 Unauthorized or 404 Not Found.

responses:
  200:
    description: Successful operation
  401:
    description: Unauthorized
  default:    # <------
    description: Unexpected error

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The API title is specified by the info.title field. It appears at the top of API docs on SwaggerHub. Make sure the API title is descriptive and reflects the API purpose.

info:
  title: Acme Reports API   # <-------
  version: 1.0.0

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Use the info.description field to provide an overview of the API. The description can be multiline and use Markdown for rich text representation. For example, you can include information about authentication, rate limits, pagination, filtering, date and time formats, common error codes, links to additional resources (such as blog posts or external examples), and any other details that would help other developers start using your API.

info:
  title: Acme Reports API
  version: 1.0.0
  description: >-
    Use the Acme Reports API to create and schedule a variety of reports from your Acme data.
    Reports can be daily, weekly, monthly and quarterly.
    
    ## Authentication
    
    ...

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The API license lets the potential API consumers know how they are allowed to use your API. Use the info.license section to specify the license name and url. If you want an open-source license, visit https://choosealicense.com and https://opensource.org/licenses to find the most appropriate license for your needs.

info:
  title: Acme Reports API
  version: 1.0.0
  license:      # <-------
    name: Apache 2.0
    url: https://www.apache.org/licenses/LICENSE-2.0.html

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This rule requires the info.contact.email field in API definitions. For public APIs, you can provide the email address of your support or API team. For internal APIs, provide the email of the responsible team or developer.

Note: While this rule requires just info.contact.email, it is a good idea to also provide info.contact.url (for example, a link to your support portal or your Slack channel) to give your API consumers multiple options to get in touch.

info:
  title: Acme Reports API
  version: 1.0.0
  contact:
    name: Acme Support
    email: [email protected]    # <-------
    url: https://support.example.com

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SwaggerHub uses property examples to display sample requests and responses in the API docs and also to generate mock responses. Use meaningful example values to help your API consumers understand what the actual data will look like.

definitions:
  User:
    type: object
    properties:
      id:
        type: integer
        format: int64
        example: 1    # <-------
      username:
        type: string
        example: demo-user  # <-------

Note that array properties require that an array-level example should be compliant:

# Good
definitions:
  Product:
    type: object
    properties:
      categories:
        type: array
          items:
            type: string
        example:    # <------- Array example is on the same level as "type: array"
          - clothes
          - accessories

# Bad - no array-level example (item example is not enough)
definitions:
  Product:
    type: object
    properties:
      categories:
        type: array
        items:
          type: string
          example: clothes

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To comply with this rule, APIs must not have the definitions section (even if these local definitions are not used). Instead, schemas should be kept in domains and referenced using domain references.

Good:

      responses:
        200:
          description: A single inventory item
          schema:
            $ref: 'https://api.swaggerhub.com/domains/acme-org/common-models/1.0#/definitions/InventoryItem'

Bad:

      responses:
        200:
          description: A single inventory item
          schema:
            $ref: '#/definitions/InventoryItem'

definitions:
  InventoryItem:
    type: object
    ...

Note that this rule still allows inline schemas such as

      responses:
        200:
          description: An array of strings
          schema:
            type: array   # <-----
            items:
              type: string

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Channel parameter declarations cannot be empty, e.g., /given/{} is invalid.

Based on this Spectral rule.

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Query parameters and fragments shouldn't be used in channel names. Instead, use bindings to define them.

Based on this Spectral rule.

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Do not include trailing slashes in channel names, as it can cause confusion. Most messaging protocols will treat example/foo and example/foo/ as different things. Keep in mind that tooling may replace slashes (/) with protocol-specific notation (e.g., . for AMQP), therefore, a trailing slash may result in an invalid channel name in some protocols.

Based on this Spectral rule.

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The schema definition of the application headers must be of type “object”.

Based on this Spectral rule.

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The AsyncAPI object info description must be present and non-empty string. Descriptions can contain Markdown so you can implement getting started information like where to find authentication keys, and how to use them.

Based on this Spectral rule.

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The license object must specify the URL for the license. Mentioning a license is only useful if people know what the license means, so add a link to the full text for those who need it.

Based on this Spectral rule.

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The info object must include a license field.

Based on this Spectral rule.

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The schema must be the latest version, currently version 2.5.0.

Based on this Spectral rule.

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Operation objects must have a description.

Based on this Spectral rule.

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Each operation must have an operationId. OperationIDs are often used by code generators for methods, functions, etc.

Based on this Spectral rule.

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Each parameter object must include a description.

Based on this Spectral rule.

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The URL in a server object cannot end in a slash character. Some tooling doesn't strip trailing slashes off when joining the server.url to the channels, and you can get awkward URLs like mqtt://example.com/broker//pets, so it's better to not include a trailing slash.

Based on this Spectral rule.

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There must be a non-empty servers object at the root level of an AsyncAPI definition file.

Based on this Spectral rule.

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The tags object must include a description field. For example:

tags:
  - name: "Aardvark"
    description: Funny-nosed pig-head raccoon.
  - name: "Badger"
    description: Angry short-legged omnivores.
                                                

Based on this Spectral rule.

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The tags array must be defined. Defining tags allows you to add more information like a description.

Based on this Spectral rule.

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