Instead of putting optional plurals in parentheses, use either plural or singular constructions and keep things consistent throughout your docset. Choose what is most appropriate for your docset and your audience.
Not recommended: To find your API key(s), visit the Credentials page.
Recommended: To find your API key, visit the Credentials page.
Not recommended: The value of the parent depends on the value(s) of its child(ren).
Recommended: The value of the parent depends on the values of its children.