diff --git a/README.md b/README.md
index f6c32fa..48b7a56 100644
--- a/README.md
+++ b/README.md
@@ -88,6 +88,24 @@ the command in the container with the CWD mounted and then exit. Alternatively
 if you want to issue multiple commands in the container quickly, you can
 run `./psc.sh bash`.
 
+## Updating Dependendencies or the Metajelo Schema
+
+Dependencies for JavaScript are minimal and are controlled by [npm](https://docs.npmjs.com/)
+and specified in `package.json`. PureScript dependencies are controlled by
+[spago](https://github.com/purescript/spago) and specified
+in `spago.dhall`, but in some cases, packages not included in the standard package
+set must also be described in `packages.dhall`. In particular, when updating
+the Metajelo schema to be used in metajelo-ui, it will be necessary to specify
+a new version of `purescript-metajelo` (with the `purescript-` prefix dropped
+in `packages.dhall`). This can simply be done by specifying a git commit hash
+or by specifying a version in the relevant section of `packages.dhall`.
+
+See the [purescript-metajelo documentation](https://github.com/labordynamicsinstitute/purescript-metajelo#a-note-on-source-generation)
+for details.
+
+It may also be required from time to time to update other dependencies, especially
+`metajelo-web`.
+
 ## Debugging
 
 For an unminified build that is easier to debug from the browser, use
diff --git a/src/Metajelo/UI.purs b/src/Metajelo/UI.purs
index e10bbdb..dcbe1f2 100644
--- a/src/Metajelo/UI.purs
+++ b/src/Metajelo/UI.purs
@@ -772,6 +772,11 @@ getOpt ::
   Opt.Option suboption
 getOpt = Opt.getWithDefault Opt.empty
 
+
+-- Used for updating an option in the view-model, typically to inject data
+-- from higher up in the component tree to lower down.
+-- Type is something like, x? and y? need Cons/Lack constraints:
+-- Sproxy a -> Opt.option (x?) -> Boolean -> Maybe (Opt.option y?)
 updateDescOn sprxy anOpt descsOn = ((Opt.get sprxy anOpt)
   <#> (\lo -> execState (do
     get >>= Opt.maySetOptState (SProxy :: _ "descs_on") (Just descsOn)) lo