Make your web app agent-ready with WebMCP - product-minded engineering with Sarah Drasner
Shownotes
If more of your users are going to show up through an agent, this episode is for you. Kent talks with Sarah Drasner - Distinguished Engineer at Google, area tech lead for AI and the web ecosystem in Chrome - about giving agents a real interface to your product instead of brittle DOM scraping.
They cover WebMCP and semantic tooling, untrusted content hints and layered defenses against prompt injection, the accessibility upside of agents, how Google is moving from "adopt agents" to levels of autonomy, and why system design is now a skill everyone needs early.
- (00:00) - Meet Sarah Drasner, Distinguished Engineer on Chrome
- (03:21) - WebMCP and fixing the web platform
- (06:04) - Semantic tooling instead of brittle DOM scraping
- (06:58) - Agents and accessibility
- (09:57) - Untrusted content and prompt injection
- (12:38) - Product decisions inside the WebMCP spec
- (14:38) - You're not building it alone
- (15:37) - Levels of autonomy and software factories
- (17:45) - Measuring agentic changes against a control
- (19:22) - Finding the right problems to solve
- (21:41) - Prototyping with agents and adversarial reports
- (26:29) - Your comprehension can't be delegated
- (28:14) - System design is the durable skill
- (31:15) - The trust diamond: agents act for people
- (33:32) - Homework: nuance, the user, and WebMCP
- (34:39) - Kent on agents that never sleep
- (37:32) - Where to follow Sarah
Sarah Drasner is a Distinguished Engineer at Google working in Chrome on AI and the web ecosystem, and she spends a lot of her time deep in WebMCP. Before that she led web, Android, iOS, observability, and reliability across Google's core infrastructure.
The through-line is that agents are not just random bots - they are often an extension of a person trying to get an outcome. WebMCP lets your site expose structured tools for coarse-grained functionality, which is more token efficient than scraping and safer because you can mark content as untrusted, read-only, or consequential. But no single protection is enough: like accessibility and security on the web, you need layered approaches.
They also talk about product decisions inside the spec itself (like keeping state across page navigations with continuation tokens), working with the people around you instead of doing it alone, measuring agentic changes against a control at Google, prototyping with agents and adversarial reports, why your comprehension can't be delegated, and why system design matters much earlier in your career now that you're making decisions with an agent in the planning loop.
Homework: keep nuance open, put the user first (even when an agent is acting for them), and go check out WebMCP.
Homework
- Keep nuance open: don't reach for one Boolean answer - plan for layered protections, because no single solution covers every case.
- Put the user first, including when an agent is acting on their behalf. Ask when they want a signal and when that signal gets tiring.
- Check out the WebMCP spec, hand it to your agent, and ask how your product can take advantage of it.
Resources
- WebMCP spec
- WebMCP on GitHub (explainer, issues, proposals)
- Chrome DevTools MCP (DevTools for agents)
- NotebookLM
- Sarah's website
- Sarah on X
- Sarah on Bluesky
- Sarah on GitHub
Guest: Sarah Drasner
Host: Kent C. Dodds
Kapitel (17)