diff --git a/app/src/client.js b/app/src/client.js
index 2cda0643..2b19f120 100644
--- a/app/src/client.js
+++ b/app/src/client.js
@@ -1,3 +1,7 @@
+/**
+ * Client-side entry point to shared frontend React App
+ *
+ */
 import BrowserRouter from 'react-router-dom/BrowserRouter';
 import React from 'react';
 import { hydrate } from 'react-dom';
diff --git a/app/src/index.js b/app/src/index.js
index 7d7bea5d..a31d2560 100644
--- a/app/src/index.js
+++ b/app/src/index.js
@@ -1,3 +1,7 @@
+/**
+ * Load server and listen
+ *
+ */
 import app from './server';
 import http from 'http';
 
diff --git a/app/src/server.js b/app/src/server.js
index 1ff16116..9bce6118 100644
--- a/app/src/server.js
+++ b/app/src/server.js
@@ -1,3 +1,9 @@
+/**
+ * Server-side Express application
+ * - API methods
+ * - entry-point to shared React App
+ *
+ */
 import React from 'react';
 import { StaticRouter } from 'react-router-dom';
 import express from 'express';
diff --git a/app/src/tile.js b/app/src/tile.js
index f3705492..7e075d21 100644
--- a/app/src/tile.js
+++ b/app/src/tile.js
@@ -1,3 +1,7 @@
+/**
+ * Tile-rendering helpers
+ *
+ */
 import path from 'path';
 import mapnik from 'mapnik';
 import SphericalMercator from '@mapbox/sphericalmercator';
diff --git a/app/src/tileserver.js b/app/src/tileserver.js
index f8e0e84e..7d5159e9 100644
--- a/app/src/tileserver.js
+++ b/app/src/tileserver.js
@@ -1,3 +1,7 @@
+/**
+ * Tileserver routes for Express app
+ *
+ */
 import express from 'express';
 
 import { get_bbox, render_tile } from './tile';