diff --git a/javascript/net/grpc/web/generictransportinterface.js b/javascript/net/grpc/web/generictransportinterface.js
index d73aae2c..790c45d9 100644
--- a/javascript/net/grpc/web/generictransportinterface.js
+++ b/javascript/net/grpc/web/generictransportinterface.js
@@ -16,13 +16,10 @@
  *
  */
 /**
- * @fileoverview gRPC web client Readable Stream
+ * @fileoverview gRPC-Web generic transport interface
  *
- * This class is being returned after a gRPC streaming call has been
- * started. This class provides functionality for user to operates on
- * the stream, e.g. set onData callback, etc.
- *
- * This wraps the underlying goog.net.streams.NodeReadableStream
+ * This class provides an abstraction for the underlying transport
+ * implementation underneath the ClientReadableStream layer.
  *
  * @author stanleycheung@google.com (Stanley Cheung)
  */
diff --git a/javascript/net/grpc/web/interceptor.js b/javascript/net/grpc/web/interceptor.js
index 46d6a00c..44e044d7 100644
--- a/javascript/net/grpc/web/interceptor.js
+++ b/javascript/net/grpc/web/interceptor.js
@@ -1,5 +1,13 @@
 /**
- * @fileoverview grpc-web Interceptor.
+ * @fileoverview grpc-web client interceptors.
+ *
+ * The type of interceptors is determined by the response type of the RPC call.
+ * gRPC-Web has two generated clients for one service: 
+ * FooServiceClient and FooServicePromiseClient. The response type of
+ * FooServiceClient is ClientReadableStream for BOTH unary calls and server
+ * streaming calls, so StreamInterceptor is expected to be used for intercepting
+ * FooServiceClient calls. The response type of PromiseClient is Promise, so use
+ * UnaryInterceptor for PromiseClients.
  */
 
 goog.module('grpc.web.Interceptor');
@@ -11,6 +19,18 @@ const Request = goog.require('grpc.web.Request');
 const UnaryResponse = goog.require('grpc.web.UnaryResponse');
 
 /**
+ * Interceptor for RPC calls with response type `UnaryResponse`.
+ * An example implementation of UnaryInterceptor
+ * <pre>
+ * TestUnaryInterceptor.prototype.intercept = function(request, invoker) {
+ *   const newRequest = ...
+ *   return invoker(newRequest).then((response) => {
+ *     // Do something with response.getMetadata
+       // Do something with response.getResponseMessage
+ *     return response;
+ *   });
+ * };
+ * </pre>
  * @interface
  */
 const UnaryInterceptor = function() {};
@@ -28,6 +48,14 @@ UnaryInterceptor.prototype.intercept = function(request, invoker) {};
 
 
 /**
+ * Interceptor for RPC calls with response type `ClientReadableStream`.
+ *
+ * Two steps to create a stream interceptor:
+ * <1>Create a new subclass of ClientReadableStream that wraps around the
+ * original stream and overrides its methods. <2>Create a new subclass of
+ * StreamInterceptor. While implementing the
+ * StreamInterceptor.prototype.intercept method, return the wrapped
+ * ClientReadableStream.
  * @interface
  */
 const StreamInterceptor = function() {};