Show HN: A guestbook with no input boxes

Fillo.so launched an agent-native guestbook that removes traditional HTML input boxes entirely, replacing them with an interface built for AI agents to interact with, according to a Show HN post by author jafu on August 19, 2026.

The demo, hosted at fillo.so/agent-guestbook, is framed as a proof-of-concept for rethinking how companies collect information — contact forms, surveys, and onboarding flows — in a world where AI agents increasingly act on behalf of users. Rather than having an agent parse and interact with conventional form fields, the site prepares the interface specifically for agent consumption.

The creator shared a concrete benchmark in the HN post: having agents fill out traditional HTML forms was 5x more token- and time-consuming than using a form surface purpose-built for agents. That figure is the project's central claim and comes solely from jafu's own testing — no third-party validation is cited.

The underlying question jafu poses is whether the standard paradigm of web forms needs to change as agents become common intermediaries between users and services. The argument is that form fields designed for humans — text inputs, dropdowns, checkboxes — create unnecessary friction and cost when an agent must interpret and manipulate them, and that a new interaction model could reduce that overhead significantly.

No company background, team size, funding, or geographic location is mentioned in the source material. The project appears to be an early-stage or solo exploration shared directly with the Hacker News community for feedback, with no comments recorded at the time of posting.