## Problem/Motivation Items inside a `ListInputDefinition` input bypass constraint validation entirely, so tools receive type-invalid item values and the invoker correction loop never fires. This is the companion gap to #3582960 (multiple inputs validating only their first item) and is **not** fixed by that issue's MR: `validateInputValue()` branches on `$definition->isMultiple()`, but a `ListInputDefinition` has `isMultiple()` FALSE with data type `list`, so it falls to the `Context::validate()` path, which does not surface item-level violations. Reproduction (kernel, verified on the #3582960 MR branch): `coercion_test_tool` has `numbers`, a `ListInputDefinition` with integer items. `validateInputValue($definition, ['not an int', 5])` returns **0 violations**, and `execute()` runs with the raw string as an item value. By contrast, invalid scalar inputs fail correctly. The gap became more costly with #3582971: an unvalidated garbage item that crashes inside `doExecute()` now surfaces as the generic logged-exception message ("Tool execution failed: TypeError. The full error has been logged.") with no violation detail and no input name — a dead end for the LLM correction loop. Input coercion (#3582973) masks the gap for recoverable shapes, and its own comments explicitly defer rejection to "typed-data validation" — a hand-off that never happens on this path. Values sourced from configuration or defaults skip the transform pipeline entirely, making validation their only gate. ## Proposed resolution - In `validateInputValue()`, treat list-typed definitions (`getDataType() === 'list'`) like multiple ones: validate each item against the list's item definition, accumulating violations across all items (post-#3582960 semantics). - Include the item position in item-level violation messages (e.g. "Input numbers (item 2): This value should be an integer.") so a model correcting a long list knows which element to fix, instead of guessing and burning another round-trip. Apply the same delta prefix to the multiple-input branch from #3582960 while in there. - Add kernel coverage: invalid item in a `ListInputDefinition` fails with the position named; valid lists pass; nested lists inside maps. - Update `InputTypeCoercionTest::testJsonShapeMismatchForList`, which currently documents the lenient behavior (a JSON-object string wrapped into an integer list executes successfully) — after this fix that case must fail validation. ## AI usage (if applicable) - [x] **AI Assisted Issue:** This issue was generated with AI assistance, but was reviewed and refined by the creator. - [ ] **AI Assisted Code:** This code was mainly generated by a human, with AI autocompleting or parts AI generated, but under full human supervision. - [ ] **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.