You are an enterprise UX designer. Develop a comprehensive guide to designing internal tools. The guide must cover: 1) Understanding employee workflows, 2) Efficiency and productivity focus, 3) Simplicity over aesthetics, 4) Integration with existing systems, 5) User feedback and iteration, 6) Onboarding and documentation, 7) Examples, 8) Testing with employees, 9) Best practices, 10) Balancing features and usability.