Add documentation on options at top of file.

ox-json.el

@@ -24,7 +24,42 @@
 
 ;;; Commentary:
 
-;;; TODO
+;;; Org mode export backend for exporting the document syntax tree to JSON.
+;;; The main entry points are `org-json-export-as-json' and
+;;; `org-json-export-to-json'. It can also be used through the built-in
+;;; export dispatcher through `org-export-dispatch'.
+
+;;; Export options:
+
+;;; :json-data-type-property (string) - This the name of a property added to all
+;;;   JSON objects in export to differentiate between structured data and
+;;;   ordinary key-value mappings. Its default value is "$$data_type". Setting
+;;;   to nil prevents the property being added altogether.
+
+;;; :json-exporters - plist containing exporter functions for different data
+;;;   types. The keys appear in :json-property-types and can also be used with
+;;;   `org-json-encode-with-type'. Functions are called with the value to be
+;;;   exported and the export info plist. Default values stored in
+;;;   `org-json-default-type-exporters'.
+
+;;; :json-property-types (plist) - Sets the types of properties of specific
+;;;   elements/objects. Nested set of plists - the top level is keyed by element
+;;;   type (see `org-element-type') and the second level by property name (used
+;;;   with `org-element-property'). Values in 2nd level are keys in the
+;;;   :json-exporters plist and are used to pick the function that will export
+;;;   the property value. Properties with a type of t will be encoded using
+;;;   `org-json-encode-auto', but this sometimes can produce undesirable
+;;;   results. The "all" key contains the default property types for all element
+;;;   types. This option overrides the defaults set in
+;;;   `org-json-default-property-types'.
+
+;;; :json-strict (bool) - If true an error will be signaled when problems are encountered
+;;;   in exporting a data structure. If nil the data structure will be exported as an
+;;;   object containing an error message. Defaults to nil.
+
+;;; :json-include-extra-properties (bool) - Whether to export node properties not listed
+;;;   in the :json-property-types option. If true these properties will be exported
+;;;   using `org-json-encode-auto'.
 
 ;;; Code: