Single tool 'fanout_tasks' has a basic schema but critical gaps in parameter descriptions and output documentation. The tool name lacks a clear action verb (should be 'start_fanout' or 'create_fanout_barrier'). Parameter descriptions are minimal (batch_id and tasks lack context on format, constraints, or expected structure). No output schema is documented, the response structure is inferred from code only. The tool combines multiple concerns (initialization + barrier setup + state tracking) without clear separation. No error handling guidance, no recovery paths, and no documentation of side effects or idempotency.

• Rename 'fanout_tasks' to 'start_fanout_barrier' or 'create_parallel_batch' to use action verb pattern (start_, create_, initialize_).
• Add parameter descriptions: batch_id (format: UUID or alphanumeric string, max 256 chars, must be unique per session), tasks (array of objects, each with required fields: subtask_id [string], input [object, optional]). Include constraint examples.
• Document output schema explicitly: {batch_id: string, branch_count: integer, status: enum[WAITING_BARRIER, IN_PROGRESS, COMPLETED, PARTIAL_FAILURE], timestamp: ISO8601}.
• Expand tool description to 150 - 250 chars: 'Initializes a parallel execution barrier for a batch of subtasks. Call this first to register all branches before executing them in parallel. Returns batch_id for use in complete_subtask() and evaluate_join() calls. Subtask IDs must be unique within the batch.'
• Add error handling: document that batch_id must be unique (return 409 Conflict if duplicate), that tasks array cannot be empty (return 400 Bad Request), and provide recovery guidance: 'If batch_id already exists, use a new UUID or call evaluate_join() to check status.'