chore: add mcp Message

Signed-off-by: He-Pin <[email protected]>

Author: He-Pin

mcp-core/src/main/java/io/modelcontextprotocol/spec/McpMessage.java

@@ -0,0 +1,40 @@
+package io.modelcontextprotocol.spec;
+
+import java.util.Map;
+import java.util.Optional;
+
+/**
+ * An MCP message base class for message driven architecture.
+ *
+ */
+public sealed interface McpMessage {
+
+	/**
+	 * @return additional metadata related to this resource.
+	 * @see <a href=
+	 * "https://modelcontextprotocol.io/specification/2025-06-18/basic/index#meta">Specification</a>
+	 * for notes on _meta usage
+	 */
+	Map<String, Object> meta();
+
+	sealed interface McpEvent extends McpMessage {
+
+		record TaskCreated(McpSchema.Task task, Map<String, Object> meta) implements McpEvent {
+		}
+
+		record TaskStatusUpdated(McpSchema.Task task, Map<String, Object> meta) implements McpEvent {
+		}
+
+		record TaskProgressUpdated(String taskId, Object progressToken, Map<String, Object> meta) implements McpEvent {
+		}
+
+		record TaskResultRetrieved(Optional<String> taskId, McpSchema.CallToolResult result,
+				Map<String, Object> meta) implements McpEvent {
+		}
+
+		record TaskFailed(Optional<String> taskId, McpError error, Map<String, Object> meta) implements McpEvent {
+		}
+
+	}
+
+}