OPEN-42
A parameter failure names every failing parameter and constraint, in no order; a skip beats a failure.
What was open
CFG-9 and CFG-10 named one parameter and one constraint. When several failed, nothing said which: two clean-room implementations (K6 pilot) both picked declaration order, which is member order and carries no meaning (OPEN-23), and for several failing keywords each reported whatever its validator library returned first. With one missing skip parameter and one missing fail parameter, member order decided between skipped and failed. CFG-21 also defined missing as a key the inputs or configuration carry, where CFG-9 says no priority supplied it.
Decision
A missing-parameter failure names every missing parameter, and a validation failure names every parameter whose value failed with every constraint it failed, all in no defined order; per value, a failing type or enum still ends that value's check. Where any missing required parameter has when_missing skip, the node is skipped: a node that is not executed does not fail. CFG-21 uses CFG-9's definition of missing. The fixture outcome shape follows, and three fixtures pin the cases.