Skip to content


This document defines the specification for defining API Design Systems. It's not dependent on any format like JSON or YAML at this point.


  • version: 2021-05-07 - current version of the specification
  • info (Info)
  • principles (array[Principle]) - requirements for API principles
  • standards (array[Standard]) - requirements around standards
  • scenarios (array[Scenario]) - requirements based on scenarios

Info (object)

  • title - title of API Design System
  • description (optional) - description of the API Design System


A principle is something that's harder to build tools around. However, it's important to capture principles that help guide decisions in building APIs. See the Principles for available ones.

  • name (optional) - name used to reference them standard throughout the document
  • description (optional) - description of the principle requirement
  • iri - IRI for the principle
  • level (enum[Requirement Level])


  - iri:
    level: must
  - iri:
    level: should
  - iri:
    level: may


The best place to find available standards is at Web Concepts.

  • name (optional) - name used to reference them standard throughout the document
  • description (optional) - description of the standard requirement
  • level (enum[Requirement Level])
  • iri - IRI for the standard


  - iri: urn:ietf:rfc:7232
    level: may
  - iri: urn:ietf:rfc:7396 
    level: should


  • description (optional) - description of the scenario
  • when (Standard Identifier) - references the condition when a requirement applies
  • then (array[Requirement]) - what to do when the when condition is met

See Example for a full example using scenarios.


  • subject (Standard Identifier) - references to the standard the requirement applies to
  • level (enum[Requirement Level])
  • OneOf
  • values (array[string]) - acceptable values for the subject based on the requirement level
  • follows - reference to a name from the defined standards the subject addresses based on the requirement level

Standard Identifier (array[string])

This identifies a standard or part of a standard. It is used to define the when condition to meet along with the subject to apply the requirement to. Refer to the supported Standards page for a list of available identifiers.

Requirement Level (enum)

These requirement levels are based on RFC 2119. Please refer to the RFC for the meaning of these values.

  • must
  • must_not
  • should
  • should_not
  • may