AI agent — An AI system that doesn't just answer once but works toward a goal in a loop — taking actions, reading the results, and deciding what to do next.
agent harness — The scaffolding around a model that turns it into a working agent — the loop, the tools it can call, and the rules for when to stop.
Why it matters
Shows a concrete, evidence-based blueprint for standing up a company-wide AI agentAn AI system that doesn't just answer once but works toward a goal in a loop — taking actions, reading the results, and deciding what to do next.Full definition → in a week by building on an open-source agent harnessThe scaffolding around a model that turns it into a working agent — the loop, the tools it can call, and the rules for when to stop.Full definition → instead of a bespoke stack — useful reference architecture for teams facing the same build-vs-adopt decision.
Key quotes
“With Claude Code’s launch in late 2024, suddenly every Stripe employee wanted to build agents. But for non-engineers, the terminal, data access, and security components were significant barriers.”
LangChain
“The Deep Agents layer solves all the non-Stripey problems, so that we can focus on solving the Stripey agent problems," explained Sharadh. "You can take a bunch of middleware off the shelf. The composable skill patterns, the composite backend, it provides the right structure, but still enough flexibility.”
LangChain
“With 500+ internal MCP tools available and a growing skills library, Kai cannot load everything into context. Agent Skills ’ allowedTools lists drive dynamic tool loading, creating a two-pass system where skill selection gates tool context, rather than loading all tools upfront.”
LangChain
“With a 1024 character limit on frontmatter, the team discovered quality degradation of frontier models with more than 150 skills when combined with their system prompt.”
LangChain
“Today, 83% of Stripe uses Kai every week, across >60k sessions. Kai sees more adoption by percentage from business functions like Marketing (95%) and GTM teams (87%) than even engineering”
