[DOC] Add information about the use of ready?

doc/development/api_graphql_styleguide.md

@@ -619,6 +619,31 @@ lot of dependent objects.
 
 To limit the amount of queries performed, we can use `BatchLoader`.
 
+### Correct use of `Resolver#ready?`
+
+Resolvers have two public API methods as part of the framework: `#ready?(**args)` and `#resolve(**args)`.
+We can use `#ready?` to perform set-up, validation or early-return without invoking `#resolve`.
+
+Good reasons to use `#ready?` include:
+
+- validating mutually exclusive arguments (see [validating arguments](#validating-arguments))
+- Returning `Relation.none` if we know before-hand that no results are possible
+- Performing setup such as initializing instance variables (although consider lazily initialized methods for this)
+
+Implementations of [`Resolver#ready?(**args)`](https://graphql-ruby.org/api-doc/1.10.9/GraphQL/Schema/Resolver#ready%3F-instance_method) should
+return `(Boolean, early_return_data)` as follows:
+
+```ruby
+def ready?(**args)
+  [false, 'have this instead']
+end
+```
+
+For this reason, whenever you call a resolver (mainly in tests - as framework
+abstractions Resolvers should not be considered re-usable, finders are to be
+preferred), remember to call the `ready?` method and check the boolean flag
+before calling `resolve`!
+
 ## Mutations
 
 Mutations are used to change any stored values, or to trigger
@@ -785,7 +810,7 @@ def ready?(**args)
   end
 
   # Always remember to call `#super`
-  super(args)
+  super
 end
 ```