John F. Kennedy was just about to give an important speech to inspire the nation to rally behind the Apollo missions to the moon. Looking for a quiet place to practice before being televised live at NASA, he stepped into what he thought was one of the hangars. It turned out to be the janitor’s closet. Inside, he saw a janitor cleaning his mop. Greeting the man, President Kennedy said, “Hey, what do you do here?”

The janitor replied “Oh, Mr. President, I’m putting a man on the moon,” before rushing off to continue his work.

Was that in his job description? If not, it should have been!

This is one of Stefan Wissenbach’s favorite stories to illustrate how an engaged employee thinks about his or her work in relation to the business’s larger engaged purpose. Purpose-driven employees don’t just mop. They mop to put a man on the moon. Can you imagine how clean NASA headquarters must have been?

Job descriptions are more than just a hiring tool; they can play a huge role in retaining and engaging your employees.

But job descriptions often get short shrift. They either don’t describe enough of what the job actually entails, or they shift with the changing needs of the company or team. When job descriptions don’t match actual job expectations, it can sew the seeds of discontent and frustration for both employee and employer rather than actually drive engagement.

We see some of the worst job-description-to-actual-work disconnects in small businesses and startups because small teams necessitate wearing multiple hats.

Multiple hats are fine. That ability to stretch creatively into roles that need to be filled can be a significant draw for highly talented, multi-passionate employees. The key is to make sure everyone has the same set of expectations.

1. Clearly define roles and responsibilities

The job description is the first, and most important, opportunity to set expectations by defining the responsibilities of the job role. If you expect the role to shift, grow, or change, say that explicitly so applicants know what to expect.

And, when the role does grow or shift, give the employee a new job description that reflects their current responsibilities so everyone is on the same page.

Incidentally, before you shift an employee into new responsibilities, make sure they’re comfortable with the change. You’ll retain employees better and drive engagement when they feel that the work they do aligns with their strengths.

2. Don’t just say what – explain why

When writing a job description, include specifics on how the job supports the Engaged Purpose. Just like that NASA janitor, every employee should understand how their job contributes to the Engaged Purpose of the company. Each employee should be able to tell you exactly what they do and why – not because they memorized it, but because it makes sense to them. This helps them emotionally invest and connect to your purpose, which is what being an engaged employee is all about.

3. Involve the employee in writing their job descriptions

Even employees you’ve already hired should have their job descriptions updated. Or, you may be creating a new role within your company for a new or existing employee. Either way, invite the employee to be part of the process of drafting the job description and be sure to include their vision and goals to help drive engagement.

4. Don’t just write it and forget it – use it

Integrate job descriptions in employees’ regular performance reviews and career development coaching. Just like an Engaged Purpose is a living statement, applied to every decision and action, so should a job description be a living document of employee achievements and goals.