diff --git a/jetty-fcgi/fcgi-client/src/main/java/org/eclipse/jetty/fcgi/parser/Parser.java b/jetty-fcgi/fcgi-client/src/main/java/org/eclipse/jetty/fcgi/parser/Parser.java
index cb86d660a6f..402f3a48970 100644
--- a/jetty-fcgi/fcgi-client/src/main/java/org/eclipse/jetty/fcgi/parser/Parser.java
+++ b/jetty-fcgi/fcgi-client/src/main/java/org/eclipse/jetty/fcgi/parser/Parser.java
@@ -23,6 +23,23 @@ import java.nio.ByteBuffer;
 import org.eclipse.jetty.fcgi.FCGI;
 import org.eclipse.jetty.http.HttpField;
 
+/**
+ * <p>The FastCGI protocol exchanges <em>frames</em>.</p>
+ * <pre>
+ * struct frame {
+ *     ubyte version;
+ *     ubyte type;
+ *     ushort requestId;
+ *     ushort contentLength;
+ *     ubyte paddingLength;
+ *     ubyte reserved;
+ *     ubyte[] content;
+ *     ubyte[] padding;
+ * }
+ * </pre>
+ * <p>Depending on the {@code type}, the content may have a different format,
+ * so there are specialized content parsers.</p>
+ */
 public abstract class Parser
 {
     protected final HeaderParser headerParser = new HeaderParser();
diff --git a/jetty-fcgi/fcgi-client/src/main/java/org/eclipse/jetty/fcgi/parser/StreamContentParser.java b/jetty-fcgi/fcgi-client/src/main/java/org/eclipse/jetty/fcgi/parser/StreamContentParser.java
index a341013c2e0..ae7f7bc0419 100644
--- a/jetty-fcgi/fcgi-client/src/main/java/org/eclipse/jetty/fcgi/parser/StreamContentParser.java
+++ b/jetty-fcgi/fcgi-client/src/main/java/org/eclipse/jetty/fcgi/parser/StreamContentParser.java
@@ -24,6 +24,10 @@ import org.eclipse.jetty.fcgi.FCGI;
 import org.eclipse.jetty.util.log.Log;
 import org.eclipse.jetty.util.log.Logger;
 
+/**
+ * <p>A stream content parser parses frames of type STDIN, STDOUT and STDERR.</p>
+ * <p>STDOUT frames are handled specially by {@link ResponseContentParser}.
+ */
 public class StreamContentParser extends ContentParser
 {
     private static final Logger LOG = Log.getLogger(StreamContentParser.class);