Designing for Agents — Zeno Rocha, Resend

Latent Space's episode with Zeno Rocha, co-founder and CEO of the email-sending company Resend, which he says had 4.3 million users and 120,000 paying customers when the episode was recorded, starts from a puzzle: why do coding agents keep recommending Resend even to a team already on Cloudflare, which has its own email service, and over much larger incumbents? The episode's written introduction cites a study in which Claude Code from Anthropic named Resend first in 64 of the 102 email recommendations the researchers could extract, while SendGrid came first seven times and appeared 55 times as an alternative. The introduction's point is that the first pick matters: a developer who asks an agent to add email and accepts the patch may never get around to trying the second choice. Latent Space adds that its own, more comprehensive tracker of what AI models recommend was more competitive, with Postmark on top for most models.

The introduction points to choices that put Resend in front of both people and agents. Its first useful distribution, the introduction says, came from React Email, a library for building email templates. Resend documented how to send those templates through SendGrid, so some of Resend's code was already in a project by the time its developers wanted a different provider. Resend's pricing page has a slider for people, and adding .md to the page's URL gives an agent a plain table it can read in one request. Resend's MCP server, which lets an agent operate the service from a chat client, grew from about 20 tools at launch to more than 80 so that users can do there what they can do in the dashboard. The write-up contrasts that with Cloudflare's server, which exposes its API through two tools, and notes that a smaller tool count would not have shrunk the oversized tool result Rocha found when he opened his own sessions. Its suggestion for MCP designers is to look at the full result of a call they make every day and see how much of it the model needs.

Everything above comes from the hosts' written introduction to the episode, not the recorded conversation. Deliverability questions the page only previews are argued in the audio: for example, a provider that rewrites links through a shared click-tracking domain can see that domain blocklisted when one customer uses it for phishing, which hurts other customers' legitimate mail, and Rocha explains why Resend introduced custom tracking domains.