Relay

Agent uses filters
Agent reads the listings and creates custom filter
WebMCP status tab
Agent writes to the sellers
Agent creates comparison

Project Story

I was searching for a car on a local second-hand marketplace, and tbh, it is kind of an awful experience.

There are overwhelmingly many filters, but somehow they are still not the right ones. I kept wishing I could just filter and sort listings using my own custom criteria. Something like:

$$ score = 0.5 \times mileage + 0.3 \times price + 0.2 \times year $$

Or really anything else I care about at that particular moment.

Reading listing descriptions is also tiresome. It requires a surprising amount of focus and attention, especially when you have dozens of tabs open. Comparing cars isn't easy either. And then, once you finally have a shortlist, you still need to message sellers, ask the same questions, negotiate, keep track of replies, etc.

While struggling through all of that, I saw an ad about the WebMCP hackathon which felt completely unrelated at the moment.

At first I didn't really understand what WebMCP was or how it worked. But when I looked through the examples, it clicked, and I was basically like: "Hell, I wish marketplaces had that"

And here I am with this project.

I built Relay as a second-hand marketplace where the website stays a normal website, but an external agent can actually work with it: search and read listings, create completely custom filters and rankings, compare items, save them into collections, message sellers, and make offers.

One of the interesting challenges was making the agent feel like part of the marketplace rather than some separate chatbot bolted onto it. The agent works with the same interface the user sees, and its actions are reflected back in the UI. Building that also made me understand WebMCP much better. Before the hackathon it felt pretty abstract; after actually using it, the idea of giving agents structured access to normal websites suddenly feels very natural.

Anyway, thanks for organizing this! It was really fun to build and experiment with.