--- a/graal/com.oracle.truffle.api/src/com/oracle/truffle/api/nodes/NodeCost.java	Mon Mar 17 14:29:45 2014 +0100
+++ b/graal/com.oracle.truffle.api/src/com/oracle/truffle/api/nodes/NodeCost.java	Mon Mar 17 14:29:45 2014 +0100
@@ -24,8 +24,46 @@
  */
 package com.oracle.truffle.api.nodes;
 
+import com.oracle.truffle.api.*;
+
+/**
+ * Represents a rough estimate for the cost of a {@link Node}. This estimate can be used by runtime
+ * systems or guest languages to implement heuristics based on Truffle ASTs.
+ * 
+ * @see Node#getCost()
+ */
 public enum NodeCost {
 
-    NONE, UNINITIALIZED, MONOMORPHIC, POLYMORPHIC, MEGAMORPHIC;
+    /**
+     * This node has literally no costs and should be ignored for heuristics. This is particularly
+     * useful for wrapper and profiling nodes which should not influence the heuristics.
+     */
+    NONE,
+
+    /**
+     * This node has a {@link CompilerDirectives#transferToInterpreter()} or
+     * {@link CompilerDirectives#transferToInterpreterAndInvalidate()} as its first unconditional
+     * statement.
+     */
+    UNINITIALIZED,
+
+    /**
+     * This node represents a specialized monomorphic version of an operation.
+     */
+    MONOMORPHIC,
+
+    /**
+     * This node represents a polymorphic version of an operation. For multiple chained polymorphic
+     * nodes the first may return {@link #MONOMORPHIC} and all addtional nodes should return
+     * {@link #POLYMORPHIC}.
+     */
+    POLYMORPHIC,
+
+    /**
+     * This node represents a megamorphic version of an operation. This value should only be used if
+     * the operation implementation supports monomorphism and polymorphism otherwise
+     * {@link #MONOMORPHIC} should be used instead.
+     */
+    MEGAMORPHIC;
 
 }