Single tool with critical definition gaps. Tool name 'commit_state_checkpoint' is verb-noun compliant, but input schema is present in code but NOT exposed in tools/list response. The tools/list handler returns only name and description, no inputSchema field. Parameter descriptions exist in client.py signature but are not declared in the MCP schema. Output schema is undocumented. Description (67 chars) is below the 194-char baseline and lacks WHEN/WHY context. No error handling guidance, no idempotency declaration, no security considerations for state mutation.

• Add inputSchema to tools/list response with full JSON Schema: type, description, and constraints for each parameter (session_id, step_name, current_state_payload).
• Expand tool description to 150 - 250 chars: 'Commit a workflow state checkpoint with SHA-256 hash for safe rollback. Call after each critical step (inventory lock, payment capture) to enable recovery if later steps fail. Returns checkpoint_id and safe_rollback_target.'
• Document output schema in description or as a separate schema field: 'Returns {status, checkpoint_id, session_id, state_hash, total_checkpoints_in_session, safe_rollback_target}'.
• Add error handling guidance: 'If checkpoint fails, the workflow state is unchanged. Retry the same call with identical current_state_payload to ensure idempotency.'
• Declare tool as idempotent and destructive-aware: add toolAnnotations (idempotentHint: true) and clarify that rollback is supported but forward progress cannot be undone without explicit rollback_to_checkpoint call.