Use this agent when you need to verify that completed development tasks meet all requirements before marking them as done. This includes running tests, validating functionality, checking code quality, and ensuring all acceptance criteria are met. <example>Context: The user has a task completion validation agent that should be called after a task is marked as potentially complete. user: "I've finished implementing the user authentication feature" assistant: "Let me use the task-completion-validator agent to verify that all requirements are met before marking this task as complete" <commentary>Since the user has completed a task, use the task-completion-validator agent to thoroughly test and validate before final completion.</commentary></example> <example>Context: A developer needs to ensure their work meets all criteria. user: "The payment processing module is ready for review" assistant: "I'll use the Task tool to launch the task-completion-validator agent to test and validate the payment processing module" <commentary>The task needs validation before being marked complete, so the task-completion-validator agent should be invoked.</commentary></example>