diff --git a/kerchunk/__init__.py b/kerchunk/__init__.py
index 398482ca..efd19771 100644
--- a/kerchunk/__init__.py
+++ b/kerchunk/__init__.py
@@ -10,3 +10,15 @@
     __version__ = "9999"
 
 __all__ = ["__version__"]
+
+
+def set_reference_filesystem_cachable(cachable=True):
+    """While experimenting with kerchunk and referenceFS, it can be convenient to not cache FS instances
+
+    You may wish to call this function with ``False`` before any kerchunking session; leavnig
+    the instances cachable (the default) is what end-users will want, since it will be
+    more efficient.
+    """
+    import fsspec
+
+    fsspec.get_filesystem_class("reference").cachable = cachable
diff --git a/kerchunk/combine.py b/kerchunk/combine.py
index 3836c12c..12a37ba5 100644
--- a/kerchunk/combine.py
+++ b/kerchunk/combine.py
@@ -157,6 +157,38 @@ def append(
         target_options=None,
         **kwargs,
     ):
+        """
+        Update an existing combined reference set with new references
+
+        There are two main usage patterns:
+
+        - if the input ``original_refs`` is JSON, the combine happens in memory and the
+          output should be written to JSON. This could then be optionally converted to parquet in a
+          separate step
+        - if ``original_refs`` is a lazy parquet reference set, then it will be amended in-place
+
+        If you want to extend JSON references and output to parquet, you must first convert to
+        parquet in the location you would like the final product to live.
+
+        The other arguments should be the same as they were at the creation of the original combined
+        reference set.
+
+        NOTE: if the original combine used a postprocess function, it may be that this process
+        functions, as the combine is done "before" postprocessing. Functions that only add information
+        (as as setting attrs) would be OK.
+
+        Parameters
+        ----------
+        path: list of reference sets to add. If remote/target options would be different
+            to ``original_refs``, these can be as dicts or LazyReferenceMapper instances
+        original_refs: combined reference set to be extended
+        remote_protocol, remote_options, target_options: referring to ``original_refs```
+        kwargs: to MultiZarrToZarr
+
+        Returns
+        -------
+        MultiZarrToZarr
+        """
         import xarray as xr
 
         fs = fsspec.filesystem(