API Standardization

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API Standardization helps ensure that your API definitions comply with your company’s API style guide. SwaggerHub provides various rules to check the operations, parameters and model definitions for compliance. Inconsistencies can be detected and fixed early in the API design process, before the actual implementations are developed and go live.

In addition to the SwaggerHub API standardization rules, you can create custom rules.

Availability

API Standardization is available for organizations on the Enterprise plan. You can see your organization plan on the Plan tab in the Organization Settings. If you are interested in upgrading to the Enterprise plan, please contact us for details.

AsyncAPI standardization is not supported in SwaggerHub On-Premise.

Organization-level OpenAPI Standardization is available in SwaggerHub On-Premise v. 1.19.2 and later. Earlier versions of SwaggerHub On-Premise include similar API-level Style Validation for OpenAPI.

Enable API Standardization and choose rules to apply

Organization owners can enable and configure API Standardization in the organization settings:

  1. Go to My Hub and click next to the organization name in the sidebar.

    – or –

    In SwaggerHub On-Premise 1.21 and earlier: click your username and select Settings. Then switch to the My Organizations tab and click Details next to the organization name.

  2. Switch to the Standardization tab.

  3. Select Enable API Standardization for this Organization.

    Enable API Standardization for this Organization

  4. Select the rules to apply or add your own rules.

    You will be able to change the selected rules at any time later.

  5. (Optional.) To prevent organization members from publishing non-compliant APIs, select Require API to pass Standardization to be publishable.

  6. (Optional.) To specify if designers can see Standardization errors in the editor page and validation panel, select Allow Designers to view Standardization errors in the Editor page.

  7. Click Save at the top right.

After you click Save, SwaggerHub will scan your organization’s APIs for compliance with the selected rules. The scan may take some time depending on the number and size of your organization’s API definitions.

After the organization-wide scan is complete, individual APIs will be re-scanned when organization members do the following:

  • Save an API in the SwaggerHub Editor.

  • Change the default version of an API.

  • Create, import or fork an API in the organization.

Create custom rules

See Custom Rules for API Standardization.

View results

Applies to: Organization Owners, Designers, non-member collaborators with the Designer role.

Organization-owned APIs that do not comply with standardization rules are displayed with the { } ERROR and { } WARNING badges in MY hub (or with a red "Standardization failed" badge if you use SwaggerHub On-Premise). You can also use the Standardization filter to find non-compliant APIs.

Viewing API Standardization errors

To view the error list, open an API in the SwaggerHub editor and check the Validation panel at the bottom.

API Standardization errors in SwaggerHub editor

Important

API Standardization scan is performed on save. This is different from the normal syntax validation which is performed dynamically as you make changes in the editor.

Automated standardization

This information applies to SwaggerHub SaaS, SwaggerHub On-Premise 1.26 and later.

You can automate standardization checks and get the error list by using SwaggerHub CLI and Registry API.

Using CLI

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:

  • 0 - no errors or warnings

  • 0 - warnings but no errors

  • 1 - at least one CRITICAL error

  • 2 - generic error (for example, the specified API was not found)

Using Registry API

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

Import and Export of Rules

Spectral file format. You can use this to share rules across different organizations and externally.

Spectral is a free tool that checks your APIs for errors and helps you improve them. It can help you improve your APIs' quality, consistency, and security. It is easy to use and can be integrated into your existing development workflow as a valuable tool for anyone who designs, develops, or tests APIs. SwaggerHub supports some of the Core Functions listed here:

  • pattern

  • alphabetical

  • casing

  • defined

  • length

  • truth

  • falsey

  • xor

  • enumeration

Here is also a list that shows SwaggerHub support for Spectral ruleset properties:

Table 1. Supported Sectral ruleset properties

Full support

message

formats

description

Partial support

given

then

severity

then.function

No support

recommended

resolved

extends

overrides

aliases

documentationUrl

parserOptions



To import the rules:

  1. Go to the Organization settings for the organization you want to import the rules into.

  2. Click the Standardization section.

  3. Click Import Rules, enter a path or URL, or browse to select a file in the Spectral format and Upload the file.

    Note

    The import files must be in YAML or JSON format and cannot be larger than 15MB.

  4. In the dialog, select options for importing rules:

    • Sync enabled/disabled to imported rules – This imports all custom rules, enabled and disabled, and all selected system rules.

    • Enable all imported rules – This imports and enables all disabled custom rules from the source organization and all selected system rules.

    • Only add rules (do not enable) –This imports all custom rules, without enabling them.

  5. Click Import.

We do not support Custom functions, but we support some Core Functions.

Disable API Standardization

API Standardization is disabled automatically when an organization’s Enterprise plan is canceled.

If you need to disable it manually:

  1. Go to My Hub and click next to the organization name in the sidebar.

    – or –

    In SwaggerHub On-Premise 1.21 and earlier: click your username and select Settings. Then switch to the My Organizations tab and click Details next to the organization name.

  2. Switch to the API Standardization tab.

  3. Clear the Enable API Standardization for this Organization check box. There is no need to unselect individual rules.

  4. Click Save.

Rules

SwaggerHub includes the following built-in standardization rules. You can also create custom rules.

OpenAPI (All)

operationId must be present and non-empty string

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.

Note

operationId values must be unique within an API definition.

↑ Back to the rule list

Operation summary must be present and non-empty string

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.

REST API operation summary and description in OpenAPI and SwaggerHub

↑ Back to the rule list

Summary should start with upper case and end with a dot

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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Operation description must be present and non-empty string

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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Operation must have a tag and non-empty string

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:

  • API documentation displays the operations grouped by tags, which helps navigate and organize large APIs.

  • Some code generators use tags to name the source code files and group operations into the same source file. For example, all operations with the payments tag may be generated in the PaymentsApi class file.

Note

Unlike the next rule, this one allows multiple tags per operation.

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Operation must have one and only one tag

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     # <-----

↑ Back to the rule list

Operation must have at least one 2xx response

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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Operation must have a default response

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

↑ Back to the rule list

API title must be present and non-empty string

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

↑ Back to the rule list

API description must be present and non-empty string

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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API license must be present and non-empty string

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

↑ Back to the rule list

API contact must be present and non-empty string

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

↑ Back to the rule list

OpenAPI 2.0 (Swagger 2.0)

All model properties must have examples

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

↑ Back to the rule list

API must not have local definitions (i.e. only $refs are allowed)

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

↑ Back to the rule list

AsyncAPI

Channel path must not have empty parameter substitution pattern

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

Based on this Spectral rule.

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Channel path must not include query ("?") or fragment ("#") delimiter

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

Based on this Spectral rule.

↑ Back to the rule list

Channel path must not end with slash

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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Headers schema type must be object

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

Based on this Spectral rule.

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Info description must be present and non-empty string

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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License object must include url

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.

↑ Back to the rule list

Info object must have license object

The info object must include a license field.

Based on this Spectral rule.

↑ Back to the rule list

AsyncAPI schema must be latest version (2.5.0)

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

Based on this Spectral rule.

↑ Back to the rule list

Operation description must be present and non-empty string

Operation objects must have a description.

Based on this Spectral rule.

↑ Back to the rule list

Operation must have operationId

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

Based on this Spectral rule.

↑ Back to the rule list

Parameter objects must have description

Each parameter object must include a description.

Based on this Spectral rule.

↑ Back to the rule list

Server URL must not end with slash

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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AsyncAPI object must have non-empty servers object

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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Tag object must have description

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.

↑ Back to the rule list

An AsyncAPI object must have non-empty tags array

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

Based on this Spectral rule.

↑ Back to the rule list

See Also

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