Inside the AI boom that's transforming how consultants work at McKinsey, BCG, and Deloitte

Lakshmi Varanasi

Sun, Apr 27, 2025, 1:44 PM 10 min read

• Consulting firms are rapidly adopting AI tools to enhance efficiency and innovation.

• Firms say that workers were ambivalent about AI at first.

• Now, they say AI has helped workers save time, which they reinvest in more advanced work.

It wasn't long ago that young consultants at McKinsey & Company would pore over reports to ensure they aligned with the firm's writing style.

Now, an AI agent called "Tone of Voice" does that.

At Boston Consulting Group, consultants now use a tool called Deckster to reduce the time they spend polishing PowerPoint slides. At Ernst & Young, instead of contacting payroll, consultants can ask a chatbot to explain their pay slips.

Consulting firms are among the early leaders of the generative AI craze. They're helping other companies train employees, develop new tools, and regulate the technology.

They are also testing generative AI internally, and in just the past two years, they've unveiled a new suite of chatbots, agents, and applications that have quickly and quietly changed how consultants do their work.

At McKinsey, consultants are using an in-house generative AI chatbot called Lilli. It synthesizes the firm's entire body of intellectual property, which spans 100 years and over 100,000 documents and interviews, the firm told BI.

Users enter their requests into Lilli, which aggregates the key points, identifies five to seven relevant internal content pieces, and points users to appropriate experts within the firm. Users can opt to have queries answered by the firm's internal knowledge repository or external sources.

Lilli's usage at the firm has exploded since it was first rolled out in 2023. Over 70% of the firm's 45,000 employees now use the tool. Those who use it turn to it about 17 times a week, McKinsey senior partner Delphine Zurkiya told BI.

When McKinsey first launched Lilli, employees experienced what the firm calls "prompt anxiety," or uncertainty over what to ask the bot. But it found that just one hour of training improved employee engagement. Zurkiya said the tool has also evolved since its launch. It wasn't initially designed to parse PowerPoints, where most of the firm's knowledge exists.

Now, McKinsey consultants told BI they use it for research, summarizing documents, analyzing data, and brainstorming. In a case study published on its website, the firm reported that workers saved 30% of their time using Lilli.

Zurkiya, who describes herself as "one of the heavy users of Lilli," said she often uses it with teams to identify the right approach to solving client problems. "We almost have AI in the room with us because we are often saying, oh, what does Lilli think," she said.