### Problem/Motivation Five small signature/semantic mistakes that are one-to-five-line fixes today and BC breaks after RC1. Batched because none warrants its own issue. 1. **`getInputDefinition(): InputDefinitionInterface|InputException`** (src/TypedInputsInterface.php:55 and the trait): the exception is thrown, never returned. The union forces consumers to handle an impossible return. Fix: `: InputDefinitionInterface` + `@throws`. 2. **`ExecutableResult` nullable context values**: constructor and `success()`/`failure()` accept `?array $contextValues` but `getContextValues(): array` returns it unguarded → `TypeError` when constructed with explicit NULL. Fix: non-nullable `array $contextValues = []`. 3. **`InputDefinition::create()` inheritance is broken**: the inherited `ContextDefinition::create($data_type)` either `ArgumentCountError`s (constructor requires `$label`/`$description`) or, for `entity:*` types, returns a core `EntityContextDefinition` that does not implement `InputDefinitionInterface`. Fix: override `create()` in `InputDefinition` and `EntityInputDefinition`. 4. **`prepareExecutableValue()` is public interface API** (src/TypedInputsInterface.php:96): it is an internal template-method hook with a stringly-typed `$source`. Fix: remove from the interface, make protected (or mark `@internal`); consider an enum for `$source`. 5. **`ToolOperation::Transform` idempotency contradiction** (src/Tool/ToolOperation.php): documented as non-modifying ("without persisting changes", `isModifying()` = FALSE) yet `isIdempotent()` returns FALSE. A non-modifying operation is by definition safe to repeat; AI consumers deciding confirmation policy will over-prompt. Fix: move `Transform` to the idempotent arm. Also: align `TypedInputsTrait` parameter types with the interface where they drifted (e.g. untyped `$skip_validation`). ### Proposed resolution One MR; each item is independently revertable. Kernel test additions only where behavior changes (items 2, 3, 5). ### API changes All five are corrections to signatures/semantics that are broken or contradictory today; this is the last release window where they can change without BC handling. ### AI usage (if applicable) - [x] **AI Assisted Issue:** This issue was generated with AI assistance, but was reviewed and refined by the creator. - [x] **AI Assisted Code:** This code was mainly generated by a human, with AI autocompleting or parts AI generated, but under full human supervision. - [x] **AI Generated Code:** This code was mainly generated by an AI with human guidance, and reviewed, tested, and refined by a human. - [ ] **Vibe Coded:** This code was generated by an AI and has only been functionally tested.