diff --git a/sge/dump-cluster-info.py b/sge/dump-cluster-info.py
index 49f4e05..5e6b78d 100755
--- a/sge/dump-cluster-info.py
+++ b/sge/dump-cluster-info.py
@@ -6,6 +6,49 @@
 # A tool that dumps every possibly imaginable info I want to get from
 # a SGE-managed cluster.
 
+"""
+This is a tool that dumps every possible imaginable info I want to get from
+a SGE-managed cluster.
+This tool runs at user-level, so can only gather information that an
+ordinary user can mine from the cluster.
+
+Currently the info available for dumping are:
+
+- cpufreq
+- lscpu
+- lspci
+- free memory (the `free` command)
+- uname
+- dmesg
+- mount
+- df
+
+
+Typical workflow
+----------------
+
+As a starter, use routine `Gather_all` to gather all information bits
+from the compute nodes. This is an expensive gather operation; it may
+take a while to complete.
+
+There is a tool called `test_accessible_hosts` to read the list of
+nodes from `qhost` SGE command, then checks the availability of every
+node by performing ssh into each one.
+
+
+Analysis: CPU variety
+---------------------
+
+To summarize the kinds of CPUs available on the compute nodes, as well
+as listing the nodes that have them, use `summarize_cpu` and
+`print_summarize_cpu`.
+This tool requires that the output of `gather_cpuinfo` has been saved
+to `cluster-info/$HOSTNAME/cpuinfo.txt` files`, where $HOSTNAME stands
+for the host basename (without domain qualifier) for every compute
+node.
+The routine that does them all is `analyze_cpu_composition`.
+"""
+
 import os
 import re
 import subprocess
@@ -291,6 +334,20 @@ def tally_summarize_cpu(summary):
 
 
 def analyze_cpu_composition():
+  """Performs analysis of the CPU composition of an SGE cluster.
+  Automatically queries the up (available) nodes and gathers the cpuinfo,
+  if it is necessary.
+  """
+  global NODE_GOOD_LIST, NODE_BAD_LIST
+  global ROOT_DIR
+  getfile = lambda H, bn: os.path.join(ROOT_DIR, H.split('.')[0], bn)
+  if len(NODE_GOOD_LIST) == 0:
+    print("Warning: need to test node accesibility...")
+    NODE_GOOD_LIST, NODE_BAD_LIST = test_accessible_hosts()
+  if not os.path.exists(getfile(NODE_GOOD_LIST[0], "cpuinfo.txt")):
+    print("Warning: need to gather cpuinfo...")
+    # Most likely you haven't run gather_cpuinfo then...
+    gather_cpu_info(NODE_GOOD_LIST)
   summ = summarize_cpu(NODE_GOOD_LIST)
   print_summarize_cpu(summ)
 
@@ -327,4 +384,3 @@ def Gather_all():
   print("\nGathering df...")
   gather_df(NODE_GOOD_LIST)
 
-