diff --git a/doc/site/modules/io/directory.markdown b/doc/site/modules/io/directory.markdown
new file mode 100644
index 00000000..0e41a33b
--- /dev/null
+++ b/doc/site/modules/io/directory.markdown
@@ -0,0 +1,10 @@
+^title Directory Class
+
+A directory on the file system.
+
+## Static Methods
+
+### Directory.**list**(path)
+
+Lists the contents of the directory at `path`. Returns a sorted list of path
+strings for all of the contents of the directory.
diff --git a/doc/site/modules/io/file.markdown b/doc/site/modules/io/file.markdown
index b9b690cd..60a23f63 100644
--- a/doc/site/modules/io/file.markdown
+++ b/doc/site/modules/io/file.markdown
@@ -1,7 +1,66 @@
 ^title File Class
 
-**TODO**
+Lets you work with files on the file system. An instance of this class
+represents an open file with a file descriptor.
+
+When you are done with a file object, it's a good idea to explicitly close it.
+If you don't, the GC will close it when the file is no longer used and gets
+finalized, but that may take a while. In the meantime, leaving it open wastes
+a file descriptor.
+
+## Static Methods
+
+### File.**open**(path, fn)
+
+Opens the file at [path] and passes it to [fn]. After the function returns, the
+file is automatically closed.
+
+    :::wren
+    File.open("words.txt") {|file|
+      file.readBytes(5)
+    }
+
+### File.**read**(path)
+
+Reads the entire contents of the file at [path] and returns it as a string.
+
+    :::wren
+    File.read("words.txt")
+
+The encoding or decoding is done. If the file is UTF-8, then the resulting
+string will be a UTF-8 string. Otherwise, it will be a string of bytes in
+whatever encoding the file uses.
+
+### File.**size**(path)
+
+Returns the size in bytes of the contents of the file at [path].
+
+## Constructors
+
+### File.**open**(path)
+
+Opens the file at [path] for reading.
 
 ## Methods
 
-**TODO**
+### **descriptor**
+
+The numeric file descriptor used to access the file.
+
+### **isOpen**
+
+Whether the file is still open or has been closed.
+
+### **size**
+
+The size of the contents of the file in bytes.
+
+### **close**()
+
+Closes the file. After calling this, you can read or write from it.
+
+### **readBytes**(count)
+
+Reads up to [count] bytes starting from the beginning of the file.
+
+(Allowing an offset to read elsewhere from the file isn't implemented yet.)
diff --git a/doc/site/modules/io/index.markdown b/doc/site/modules/io/index.markdown
index ba41efbd..1dc81f49 100644
--- a/doc/site/modules/io/index.markdown
+++ b/doc/site/modules/io/index.markdown
@@ -1,6 +1,7 @@
 ^title Module "io"
 
-**TODO**
+Provides access to operating system streams and the file system.
 
+* [Directory](directory.html)
 * [File](file.html)
 * [Stdin](stdin.html)
diff --git a/doc/site/modules/io/stdin.markdown b/doc/site/modules/io/stdin.markdown
index 399a9af5..66377f85 100644
--- a/doc/site/modules/io/stdin.markdown
+++ b/doc/site/modules/io/stdin.markdown
@@ -1,7 +1,12 @@
 ^title Stdin Class
 
-**TODO**
+The standard input stream.
 
-## Methods
+## Static Methods
 
-**TODO**
+### **readLine**()
+
+Reads one line of input from stdin. Blocks the current fiber until a full line
+of input has been received.
+
+Returns the string of input or `null` if stdin is closed.
diff --git a/doc/site/modules/io/template.html b/doc/site/modules/io/template.html
index ab36a796..ebce39a1 100644
--- a/doc/site/modules/io/template.html
+++ b/doc/site/modules/io/template.html
@@ -27,6 +27,7 @@
     <section>
       <h2>io classes</h2>
       <ul>
+        <li><a href="directory.html">Directory</a></li>
         <li><a href="file.html">File</a></li>
         <li><a href="stdin.html">Stdin</a></li>
       </ul>
diff --git a/src/module/io.wren b/src/module/io.wren
index 9694d2f9..a4135a15 100644
--- a/src/module/io.wren
+++ b/src/module/io.wren
@@ -51,6 +51,8 @@ foreign class File {
     Scheduler.runNextScheduled_()
   }
 
+  foreign descriptor
+
   isOpen { descriptor != -1 }
 
   size {
@@ -74,7 +76,6 @@ foreign class File {
   foreign static sizePath_(path, fiber)
 
   foreign close_(fiber)
-  foreign descriptor
   foreign readBytes_(count, fiber)
   foreign size_(fiber)
 }