Which card should I use?

Why I built it

A few cards into the points hobby, I was standing in Whole Foods trying to work out whether my Prime Visa or my Amex Gold earned more there. Browser extensions can help when you shop online, but nothing helps at a register.

My first idea was a ghost card: one physical card that charges whichever of my cards is best. The card networks don't allow that, and Apple Pay is locked down. So I built the next best thing. Before I shop, I ask in plain words, and earnrate does the research.

An example from Claude with earnrate connected. The numbers are earnrate's real answer for a sample wallet.

It remembers what you've spent

Many bonus rates stop at a cap. Blue Cash Preferred pays 6% at supermarkets until you've spent $6,000 in a year, then 1%. earnrate keeps track, so the answer changes when it should.

$ earnrate whole foods 80

Use Blue Cash Preferred:
6% back, about $4.80.

  1. Blue Cash Preferred  6%
  2. Prime Visa           5%
  3. Amex Gold            4%

$ earnrate whole foods 80

Use Prime Visa:
5% back, about $4.00.

  1. Prime Visa           5%
  2. Amex Gold            4%
  Blue Cash Preferred's $6,000
  supermarket cap is used up.

earnrate's real answers, shortened. Cards that pick categories each quarter, like U.S. Bank Cash+ and Chase Freedom Flex, work the same way: earnrate uses the picks you've made.

It explains itself

Every answer shows the rule behind it. A few things it catches:

• Costco's registers only take Visa, so it won't suggest your Amex there.
• If your points are worth more to you than face value, it ranks on your number and says where the answer would flip.
• Food at a stadium or inside a hotel may not count as a restaurant. It warns you and says which card wins either way.

Ask it from Claude

earnrate runs as an MCP server, so you can ask in a chat with Claude, like the Trader Joe's example above. It can also show what's left on each cap, and record a purchase so the next answer accounts for it. Answers come back with a stable card id as well as the explanation, so an agent that pays for you can use them directly. It never needs or returns a card number.

Cards it knows

Each card's rules come from the issuer's own terms. A weekly check reloads those pages and flags anything that changed.

• American Express Gold, Platinum, Blue Cash Preferred, Blue Cash Everyday, Blue Business Plus
• Chase Sapphire Preferred, Sapphire Reserve, Freedom Unlimited, Freedom Flex, Ink Business Cash, Ink Business Preferred, Prime Visa
• Citi Strata Elite, Strata Premier, Double Cash, Custom Cash, My Best Buy Visa
• Capital One Venture X, Venture, Savor
• Wells Fargo Active Cash, Autograph
• Others U.S. Bank Cash+, Bilt Obsidian, SoFi Unlimited 2%

Nothing leaves your laptop

earnrate runs on your own machine, and your wallet is a file you control. It never asks for card numbers or bank logins, and there's no tracking. The one exception is optional and off by default: for a store it doesn't recognize, it can ask Claude what kind of store it is. Only the store's name is sent.

Get it