feat(spec)!: Add a required protocol version to the agent card.

docs/specification.md

@@ -159,6 +159,7 @@ Agent Cards themselves might contain information that is considered sensitive.
 
 | Field Name                          | Type                                                               | Required | Description                                                                                                                                 |
 | :---------------------------------- | :----------------------------------------------------------------- | :------- | :------------------------------------------------------------------------------------------------------------------------------------------ |
+| `protocolVersion`                   | `string`                                                           | Yes      | The version of the A2A protocol this agent supports.                                                                                        |
 | `name`                              | `string`                                                           | Yes      | Human-readable name of the agent.                                                                                                           |
 | `description`                       | `string`                                                           | Yes      | Human-readable description. [CommonMark](https://commonmark.org/) MAY be used.                                                              |
 | `url`                               | `string`                                                           | Yes      | Base URL for the agent's A2A service. Must be absolute. HTTPS for production.                                                               |
@@ -247,6 +248,7 @@ Describes a specific capability, function, or area of expertise the agent can pe
 
 ```json
 {
+  "protocolVersion": "0.2.9",
   "name": "GeoSpatial Route Planner Agent",
   "description": "Provides advanced route planning, traffic analysis, and custom map generation services. This agent can calculate optimal routes, estimate travel times considering real-time traffic, and create personalized maps with points of interest.",
   "url": "https://georoute-agent.example.com/a2a/v1",

specification/grpc/a2a.proto

@@ -341,6 +341,8 @@ message AgentInterface {
 // - Default modalities/content types supported by the agent.
 // - Authentication requirements
 message AgentCard {
+  // The version of the A2A protocol this agent supports.
+  string protocol_version = 16;
   // A human readable name for the agent.
   string name = 1;
   // A description of the agents domain of action/solution space.

specification/json/a2a.json

@@ -181,6 +181,13 @@
                     "description": "The transport of the preferred endpoint. If empty, defaults to JSONRPC.",
                     "type": "string"
                 },
+                "protocolVersion": {
+                    "description": "The version of the A2A protocol this agent supports.",
+                    "examples": [
+                        "0.2.5"
+                    ],
+                    "type": "string"
+                },
                 "provider": {
                     "$ref": "#/definitions/AgentProvider",
                     "description": "The service provider of the agent"
@@ -234,6 +241,7 @@
                 "defaultOutputModes",
                 "description",
                 "name",
+                "protocolVersion",
                 "skills",
                 "url",
                 "version"

types/src/types.ts

@@ -109,6 +109,11 @@ export interface AgentInterface {
  * - Authentication requirements
  */
 export interface AgentCard {
+  /**
+   * The version of the A2A protocol this agent supports.
+   * @TJS-examples ["0.2.5"]
+   */
+  protocolVersion: string;
   /**
    * Human readable name of the agent.
    * @TJS-examples ["Recipe Agent"]