Entities

Entities represent participants in the protocol: systems, services, actors, or trust domains.

Definition

{
  "entities": [
    {
      "id": "client",
      "name": "Client Application",
      "type": "client",
      "description": "Application requesting access to protected resources"
    },
    {
      "id": "auth_server",
      "name": "Authorization Server",
      "type": "authorization_server"
    }
  ]
}

Entity Fields

Field	Type	Required	Description
id	string	Yes	Unique identifier (lowercase, alphanumeric, underscores)
name	string	Yes	Human-readable display name
type	enum	Yes	Entity type classification
description	string	No	Role description

Entity Types

OAuth/OIDC Types

Type	Description
client	Application or service initiating requests
authorization_server	Issues tokens and handles authentication
resource_server	Hosts protected resources
user	Human actor / resource owner
browser	User agent / web browser

Agent Protocol Types

Type	Description
agent	AI/LLM agent
tool_server	Exposes tools via protocol (MCP)
tool	Individual tool
delegated_agent	Agent receiving delegated tasks (A2A)

Identity Types

Type	Description
identity_provider	Authenticates users (SAML IdP)
service_provider	Relies on identity provider (SAML SP)

Generic Types

Type	Description
server	Generic server
other	Custom entity type

ID Patterns

Entity IDs must match: ^[a-z][a-z0-9_]*$

Valid: client, auth_server, tool_1

Invalid: Client, auth-server, 1tool

Diagram Rendering

Entity types affect how they're rendered in diagrams:

• D2: Different shapes (person, hexagon, cylinder, etc.)
• DOT: Different node shapes
• PlantUML/Mermaid: Participant declarations