Brier

Make your shopping agent compare, explain, and ask before buying.

Brier helps your AI agent search for products, compare them against your brief, and show why one option ranks above another. Seller payment and affiliate data never improve a result's position.

Brier runs on your computer alongside the AI app you already use. There is no Brier account or cloud service.

Get started

You need Node.js 20 or later and an AI app that supports MCP. MCP is the standard the app uses to connect to tools running on your computer.

npx brier-agent init

The initializer walks you through setup and prints the configuration to add to your AI app. Once connected, try a specific brief:

Find black wool running shoes under $130. Compare price, delivery, fit, and merchant trust. Tell me why the winner ranked first and which options were ruled out.

What you get

• A ranked shortlist based on the requirements and preferences in your brief.

• Reasons for every recommendation, including tradeoffs and missing information.

• Sponsored offers labeled and placed below organic results.

• Merchant trust evidence and an honest report of which stores were searched.

• A local history you can review, correct, and use to improve later searches.

• A separate approval step before any automated checkout.

How Brier works

1. You tell your agent what you want, what matters, and your budget.

2. Brier collects candidates from the direct store connections you configured. Your agent can also pass product details from browser tools it already controls.

3. Brier checks the candidates, ranks them against your brief, and returns a shortlist with reasons and coverage gaps.

4. If you choose to buy, Brier asks you to approve the exact item, quantity, and spending limit.

Results reported from a browser are clearly marked as agent-observed. You can compare them and open the product page, but Brier will not use them for automated checkout or a background price watch until a direct store connection confirms the offer.

Store coverage

Store access varies because each platform has different rules. Brier reports a store as unavailable or blocked when it cannot search it, rather than presenting partial coverage as a complete market search.

When a native store connection is unavailable, your agent may still compare permitted product pages with browser tools it already has. Brier accepts only product facts needed for comparison. It does not take over the browser or ask for cookies, page contents, passwords, one-time codes, or your AI provider key.

Privacy and control

Brier is software you run. The repository owner does not operate a Brier service.

• Your AI provider key stays in your AI app. Store logins stay with you and the store.

• Brier does not send your searches, settings, or local history to the repository owner.

• Brier never accepts raw card details. Automated checkout can use a payment token created for the purchase, or Brier can hand you a cart to finish in your own browser.

• Search is not permission to buy. Every automated checkout needs your approval for that purchase.

Learn more

• Why Brier exists

• How ranking works

• How merchant trust works

• Privacy and software ownership

• Build from source or contribute

• Report a security issue

Brier is open source under the MIT License.