added amendment: shall not cause auto-activation
diff --git a/bundles/org.eclipse.core.runtime/src/org/eclipse/core/runtime/content/IContentDescriber.java b/bundles/org.eclipse.core.runtime/src/org/eclipse/core/runtime/content/IContentDescriber.java
index 89122fb..4e13faa 100644
--- a/bundles/org.eclipse.core.runtime/src/org/eclipse/core/runtime/content/IContentDescriber.java
+++ b/bundles/org.eclipse.core.runtime/src/org/eclipse/core/runtime/content/IContentDescriber.java
@@ -18,6 +18,15 @@
* Content describers know how to retrieve metadata from
* contents.
* <p>
+ * Note: It is expected that content describer implementations be declared in a package
+ * that is exempt from plug-in activation (using the Eclipse-AutoStart bundle
+ * manifest header). Since all describers are instantiated when the content type
+ * framework is initialized, failure in complying with this requirement causes
+ * premature activation, which must be avoided. Future implementations of the
+ * framework might refuse to instantiate describers if doing so would trigger
+ * activation of the corresponding plug-in.
+ * </p>
+ * <p>
* Describers for text-based content types should implement
* <code>ITextContentDescriber</code> instead.
* </p>
diff --git a/bundles/org.eclipse.core.runtime/src/org/eclipse/core/runtime/content/ITextContentDescriber.java b/bundles/org.eclipse.core.runtime/src/org/eclipse/core/runtime/content/ITextContentDescriber.java
index c19f33b..4d4e6ac 100644
--- a/bundles/org.eclipse.core.runtime/src/org/eclipse/core/runtime/content/ITextContentDescriber.java
+++ b/bundles/org.eclipse.core.runtime/src/org/eclipse/core/runtime/content/ITextContentDescriber.java
@@ -17,7 +17,16 @@
* Text content describers extend basic content describers to provide
* the ability of scanning character streams (readers). Describers for
* text-based content types must implement this interface
- * instead of <code>IContentDescription</code>.
+ * instead of <code>IContentDescription</code>.
+ * <p>
+ * Note: It is expected that content describer implementations be declared in a package
+ * that is exempt from plug-in activation (using the Eclipse-AutoStart bundle
+ * manifest header). Since all describers are instantiated when the content type
+ * framework is initialized, failure in complying with this requirement causes
+ * premature activation, which must be avoided. Future implementations of the
+ * framework might refuse to instantiate describers if doing so would trigger
+ * activation of the corresponding plug-in.
+ * </p>
* <p>
* Clients may implement this interface.
* </p>
