One of Facebook Messenger’s most highly awaited features, a text-based virtual assistant simply called “M,” isn’t due out for several more years. But according to Facebook VP of Messaging Products David Marcus, there’s a very good reason for that: M still has a long way to go before it’s ready for all of Facebook’s (FB) 1.7 billion members to use.

Marcus initially acknowledged as much this April, roughly eight months after the social network began testing M with a small group of Messenger users, who can access M inside the Messenger app.

In theory, Facebook wants M to one day help Facebook users accomplish day-to-day tasks like booking travel, ordering food and scheduling appointments. In an ideal world, it would also be powered by a smart set of algorithms on the back-end with very little human intervention.

Although the goal is for M to one day be almost 100% automated, the virtual assistant still heavily relies on a team of humans to complete many tasks.

“Traffic, weather or reminders are 100% automated,” Marcus recently explained to Yahoo Finance. “However, if you’re asking to organize a cruise on the Danube for a group of 12 people with specific requests, then you’re probably going to need human assistance.”

The process of getting to a point where M is entirely automated has been an interesting one for Marcus and the Messenger team.

“What we’re finding is also what we’re finding with bots,” Marcus added. “There’s a lot that we can learn in automation and conversational interfaces. But also we need to bring a lot more visual elements and buttons and all kinds of interaction and layers to actually make the experience really good.”

M is another major play for Messenger, which has rapidly evolved into a widely used messaging platform since Marcus joined Facebook following a stint at PayPal (PYPL) as president.

Not only does Messenger have 250 employees, but it also has 1 billion users who utilize it it to send payments to one another and interact with businesses via 30,000-plus bots. The platform also allows outside developers to augment the Messenger experiences with touches like stickers and animated GIFs.

Messenger’s 1 billion users is an impressive stat, to be sure, but still falls short of Facebook’s 1.7 billion user base. The goal with efforts like M is to draw even more users to Messenger, keep them engaged, and help close that gap.

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JP Mangalindan is a senior correspondent for Yahoo Finance covering the intersection of tech and business. Follow him on Twitter or Facebook.

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