diff --git a/xpcom/io/nsIPipe.idl b/xpcom/io/nsIPipe.idl
index fb8465182ab..e7b54e8e365 100644
--- a/xpcom/io/nsIPipe.idl
+++ b/xpcom/io/nsIPipe.idl
@@ -73,6 +73,22 @@ interface nsIPipe : nsISupports
 {
     /**
      * initialize this pipe
+     *
+     * @param nonBlockingInput
+     *        true specifies non-blocking input stream behavior
+     * @param nonBlockingOutput
+     *        true specifies non-blocking output stream behavior
+     * @param segmentSize
+     *        specifies the segment size in bytes (pass 0 to use default value)
+     * @param segmentCount
+     *        specifies the max number of segments (pass 0 to use default
+     *        value).   Passing PR_UINT32_MAX here causes the pipe to have
+     *        "infinite" space.  This mode can be useful in some cases, but
+     *        should always be used with caution.  The default value for this
+     *        parameter is a finite value.
+     * @param segmentAllocator
+     *        pass reference to nsIMemory to have all pipe allocations use this
+     *        allocator (pass null to use the default allocator)
      */
     void init(in boolean nonBlockingInput,
               in boolean nonBlockingOutput,