Arazzo: OpenAPI Workflows

The Arazzo Specification is a new addition to the OpenAPI Specification that allows you to define sequences of operations for your API.

An Arazzo description is a separate document that references your OpenAPI document and describes how to combine operations from your OpenAPI document into step-by-step sequences.

Arazzo descriptions are useful for:

• Defining complex sequences of operations that involve multiple API calls.
• Documenting the expected behavior of your API in a more structured way than a narrative description.
• Generating code to execute the sequences of operations.
• Generating tests to verify that the sequences of operations behave as expected.
• Generating documentation that explains how to use the sequences of operations.

Arazzo Description Structure

An Arazzo description is a JSON or YAML document that follows the structure defined by the Arazzo Specification.

Arazzo version

The version of the Arazzo Specification that the document uses. The value must be a supported version number.

Info metadata

Provides metadata about the Arazzo description.

Source description

An array of source description objects defining the OpenAPI or other documents containing the operations referenced by the workflows. The array must contain at least one source.

Workflows

An array of workflow objects defining the workflows. The array must contain at least one workflow.

This table shows all fields at the root of the Arazzo Specification:

Arazzo Specification Versions

The arazzo field contains the version number of the Arazzo Specification that the document conforms to. Tooling should use this value to interpret the document correctly.

The current version of the Arazzo Specification is 1.0.0-prerelease, but keep in mind that the specification is still under development.

Info Object

Provides metadata about the Arazzo description.

Below is an example of an info object in an Arazzo document:

Source Description Object

A source description points to an OpenAPI document containing the operations referenced by the workflows in this document. It may also reference other Arazzo documents.

Below is an example of two source description objects in an Arazzo description document:

Workflow Object

A workflow object defines a sequence of operations.

Below is an example of a workflow object:

Step Object

A step object defines a single operation to perform as part of a workflow.

Below is an example of step objects in an Arazzo description document:

Parameter Object

A parameter object defines a single parameter to pass to an operation in a workflow step.

Parameter Location

For parameters passed to an operation, the in field specifies the location of the parameter. The possible values are:

• path - The parameter is part of the operation’s URL path.
• query - The parameter is appended to the operation’s URL as a query parameter.
• header - The parameter is sent in the request headers.
• cookie - The parameter is sent in a cookie.

For parameters passed to a workflow, the in field must be omitted. Workflow parameters are always passed in the workflow’s inputs object.

Arazzo Parameter Object Examples

Success Action Object

A success action object defines an action to take when a workflow step succeeds.

Below is an example of a success action object:

Failure Action Object

A failure action object defines an action to take when a workflow step fails.

Below is an example of a failure action object:

Components Object

The components object holds reusable objects that can be referenced from other parts of the Arazzo description.

The keys in the components object may only contain alphanumeric characters, underscores, and dashes.

Arazzo Components Object Example

The components defined in an Arazzo description are scoped to that document. Components defined in one Arazzo description cannot be referenced from another Arazzo description.

Reusable Object

A reusable object allows you to reference objects like success actions and failure actions defined in the components object from locations within steps or workflows.

Arazzo Reusable Object Example

Criterion Object

A criterion object is used to specify assertions in the successCriteria field of a step object, or the criteria field of a success action object or failure action object.

Criterion objects support three types of assertions:

• simple - Basic comparisons using literals, operators, and runtime expressions. This is the default if no type is specified.
• regex - Applies a regular expression pattern to a context defined by a runtime expression.
• JSONPath - Applies a JSONPath  expression to a context defined by a runtime expression. The root node of the JSONPath is the context.

Literals

Literals are constant values that can be used in simple conditions. The following data types are supported:

Operators

Simple conditions support the following operators:

String comparisons are case-insensitive.

A criterion object consists of the following fields:

Arazzo Criterion Object Examples

Simple Condition - Check if a drink was successfully created

Simple Condition - Check if the bar is open

Regex Condition - Check if the drink name matches a pattern

JSONPath Condition - Check if the ingredient list contains “whiskey”

Simple Condition - Check if the customer is over 21

JSONPath Condition - Check if there are any available tables

Request Body Object

The request body object describes the payload and Content-Type to send with the request when executing an operation in a workflow step.

Request Body Object Examples

JSON Payload (Template)

JSON Payload (Object)

JSON Payload (Runtime Expression)

XML Payload (Template)

Form Data Payload (Object)

Form Data Payload (String)

Payload Replacement Object

A payload replacement object specifies a location within the request payload and the value to insert at that location.

Payload Replacement Object Examples

Runtime Expression Value

Literal Value

Runtime Expressions

Runtime expressions allow you to reference values that will be available when a workflow is executed, such as values from the HTTP request or response, the event that triggered the workflow, or outputs from previous workflow steps.

The syntax for runtime expressions is {expression}, where expression is one of the following:

Runtime Expression Examples

Arazzo Specification Extensions

The Arazzo Specification allows custom properties to be added at certain points using specification extensions.

Extension properties are always prefixed by "x-" and can have any valid JSON value.

For example:

The extensions defined by the Arazzo Specification are:

The specification extension key formats ^x-oai- and ^x-oas- are reserved for extensions defined by the OpenAPI Initiative .

Extension properties can be used to add additional features, metadata, or configuration options to the Arazzo description that are not directly supported by the current version of the specification. However, additional tooling may be required to process custom extensions.