One link, one box to fill in, and Gemini can search real secondhand listings.
Nothing to install. You add Secondhand MCP once from a desktop browser as a custom app for Gemini, and after that it works in Gemini on the web and on your phone. Google currently limits custom apps to Google AI Pro and AI Ultra subscribers in the US, on a personal Google account. Secondhand MCP itself has a free tier with no credit card.
Takes about two minutes, once
Under Custom apps, click Add a custom app (the first time it is a link that reads Add a custom app link to get started) and paste the address:
A Secondhand MCP sign-in window opens. Use your email (we send a one-click link) or Google, then click Allow. That creates your free account, with 10 searches a month and no card needed.
In a Gemini chat, type @, pick Secondhand, and ask for something. Copy this to start: Find a used road bike under $400 near Austin, TX
Google limits custom apps to Google AI Pro and AI Ultra subscribers in the US, on a personal Google account (not work or school), age 18 or over, with Keep Activity turned on in your Google Account. If any of those are not true yet, the section stays hidden.
Type @ in the chat box and choose Secondhand before your question. That tells Gemini to use the app for that prompt.
Check your spam folder, or go back and choose Google instead. That one is instant.
It can only search and read listings. It never posts, messages sellers, or buys anything. You sign in with your own email or Google, and you can remove the app from Connected Apps at any time.