Eight months after closing a $350 million funding round, Sierra Technologies Inc. today announced that it has raised an additional $950 million at a $15 billion valuation.

Alphabet Inc.’s GV venture capital arm and Tiger Global led the investment. They were joined by Benchmark, Sequoia, Greenoaks and several others.

Sierra was founded in early 2024 by OpenAI Group PBC board chair Bret Taylor (pictured, left) and former Google LLC executive Clay Bavor (right). The company sells tools that help organizations build artificial intelligence agents. According to Sierra, its software has been adopted by nearly half the Fortune 50 and generates $150 million in annual recurring revenue.

The platform’s core component is a developer tool called the Agent SDK. It enables software teams to create AI agents without building everything from scratch.

The tool ships with a set of prepackaged agent skills. Several focus on helping agents find the data necessary to answer user questions. Others automate more complex activities such as prioritizing technical support requests by urgency. According to Sierra, developers can mix and match skills into an automation workflow that performs multiple-step tasks.

Activating a predefined automation workflow is less complicated than generating a new plan for how to process a user request. As a result, there are fewer opportunities for AI agents to make mistakes, which can lower the risk of output errors. For added measure, Agent SDK enables developers to define guardrails that block erroneous AI output.

The tool can test a newly created agent’s output quality by simulating user interactions. After developers verify that the agent works as expected, they can integrate it with their company’s systems using a set of pre-packaged connectors.

Sierra’s connectors make it possible to give an AI assistant access to externally-hosted datasets such as knowledge bases. Furthermore, they enable agents to take actions on the user’s behalf. A software-as-a-service startup, for example, could build an agent that can switch customers to a new subscription tier without input from the support team.

Sierra sells Agent SDK alongside several other tools. There’s Agent Studio, which provides similar agent development features but doesn’t require users to write code. For customer service teams, it offers a tool called Live Assistant that generates pointers on how to process support tickets.

Under the hood, Sierra’s product portfolio is powered by more than 15 open-source and proprietary models. The company may use its new funding round to replace some of those proprietary models with custom algorithms. Several other well-funded AI startups have taken that route in a bid to reduce their inference costs. 

Photo: Sierra