feat: enforce MCP request ID validation requirements

Signed-off-by: Christian Tzolov <christian.tzolov@broadcom.com>

mcp/src/main/java/io/modelcontextprotocol/spec/McpSchema.java

@@ -236,6 +236,17 @@ public final class McpSchema {
 		@JsonProperty("method") String method,
 		@JsonProperty("id") Object id,
 		@JsonProperty("params") Object params) implements JSONRPCMessage { // @formatter:on
+
+		/**
+		 * Constructor that validates MCP-specific ID requirements. Unlike base JSON-RPC,
+		 * MCP requires that: (1) Requests MUST include a string or integer ID; (2) The ID
+		 * MUST NOT be null
+		 */
+		public JSONRPCRequest {
+			Assert.notNull(id, "MCP requests MUST include an ID - null IDs are not allowed");
+			Assert.isTrue(id instanceof String || id instanceof Integer || id instanceof Long,
+					"MCP requests MUST have an ID that is either a string or integer");
+		}
 	}
 
 	/**

mcp/src/main/java/io/modelcontextprotocol/util/Assert.java

@@ -76,4 +76,17 @@ public final class Assert {
 		return (str != null && !str.isBlank());
 	}
 
+	/**
+	 * Assert a boolean expression, throwing an {@code IllegalArgumentException} if the
+	 * expression evaluates to {@code false}.
+	 * @param expression a boolean expression
+	 * @param message the exception message to use if the assertion fails
+	 * @throws IllegalArgumentException if {@code expression} is {@code false}
+	 */
+	public static void isTrue(boolean expression, String message) {
+		if (!expression) {
+			throw new IllegalArgumentException(message);
+		}
+	}
+
 }