Zeno Rocha
On The Changelog
“I was creating maybe a competitor analysis on Claude and OpenAI. I wanted to see what they would recommend. And then they told me, like, oh, Resend is the most expensive service. And I was like, no, I know for a fact that this is not true. … So it turns out that agents don't really like JavaScript enabled sliders. They cannot slide.”
The Changelog · Hands-On Engineering Podcasts · October 2026
The Resend founder explains how he found that AI assistants were misreading his pricing page. He fixed it by serving a Markdown version through content negotiation, and says you only find problems like this by putting yourself in the agent's shoes.
Transcript
Yeah, that was funny because as you were saying good things about that page, I'm like, Yeah, that page is good, but it's good for humans. It's not right. It's terrible for agents.
…might be like. How many emails do you want? How many will you send? Is it transactional only? How many per day? You know, and all that is maybe an API call, and the response is JSON. It's like, here you go. This, or maybe it's market. Maybe it's actually Markdown. I don't know. But, anyways.
…with stuff. And then I asked, like, oh, I was creating maybe a competitor analysis on Claude and OpenAI. I wanted to see what they would recommend. And then they told me, like, oh, recent is the most expensive service. And I was like, no, I know for a fact that this is not true. Yeah. And I was like, so surprised and both of them got it wrong. And then I was like, okay, let me uncover this. So it turns out that agents don't really like JavaScript enabled sliders. They cannot slide. That's not something they're able to do. And I'm like, okay, we need a Markdown version. So I made the Markdown. I changed the alternate header. So if you were to request that with a different header, then it returns that. And then I just started to like seeing for real life. And then I just made the requests and then started to get the math right. Like all, so what I did was, okay, I'm sending…
What is that cadence for you? How frequently do you sit down in the place of the user? Is this something you have blocked in your calendar? How do you approach this, you know, must feel the pain, act as user advocate that you are?
I'm always looking for excuses. So I operate on that. So I'm like, oh, okay, we have an all-hands meeting, for example, every Monday, right? So we used to use a Notion doc where every team goes in, they write their updates, and then we go through that doc together, and that's it. So, oh, okay, this…
That's cool, man. I feel like that's definitely the way you uncover the real potential, too, right? Not only uncovering all of your blemishes that you need to fix, and you can only discover them by using it. And what a user will do is they will get frustrated and go away. Some will complain, lots…
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