Know which card to tap.
Ask your AI assistant which card to use for dinner, online shopping or a trip to Japan. With Cardex, it checks the rebate rates, caps and fine print on Hong Kong cards before it answers. No guessing, no copied comparison-site rankings.
Set it up: paste this into your AI assistant
Install the Cardex skill so you can look up Hong Kong credit-card facts. 1. Download https://cardex.brandonhk.com/skill.md and save it as cardex/SKILL.md in your skills directory. 2. Add the Cardex MCP server (streamable HTTP, no auth): https://cardex.brandonhk.com/mcp 3. If you can't install skills or MCP servers, read that skill.md now and call the endpoint over plain HTTP as it describes. Check it works: call list_tags with limit 3 and show me the result. Cardex returns facts only. You compare the cards, and you tell me which terms you couldn't verify.
No card numbers. Cardex never knows which cards you hold.
“Dinner at TamJai tonight, about $280. Red Card or WAKUWAKU?”
| Card | Dining | Back on $280 |
|---|---|---|
| HSBC Red Credit Card | 8% | $22.40 |
| AEON Card WAKUWAKU | 1% | $2.80 |
Red's 8% is a designated-merchant rate — it applies because TamJai is on the illustrative list.
Before you tap, check
- Red Card caps this rebate each month. How much have you earned so far?
- Red Card excludes Octopus top-ups. Not relevant to dinner.
- WAKUWAKU caps this rebate each month. How much have you earned so far?
Figures and open checks are Cardex's real response on the illustrative seed (as of 2026-11-01), not issuer terms. Verified records carry the terms link and last-checked date.
The hard part isn't the maths. It's the fine print.
“Is it really 8% on dining?”
The ad says 8%. The small print says listed merchants only.
“Have I hit this month's cap?”
Past the cap, the rebate is 0%.
“Did this offer need registering?”
Forget to register and you find out on your statement.
Set up once. Then just ask.
Paste the prompt
Into Claude, Cursor, or any assistant that supports skills or MCP. It installs Cardex itself.
Ask like you'd ask a friend
“Going to Japan next week, which card?”
Get the numbers and the catch
Rates, caps, registration deadlines, and anything it couldn't confirm, so your statement holds no surprises.
Your AI can already answer. Why add Cardex?
| Asking an AI chatbot as-is | With Cardex | |
|---|---|---|
| Where numbers come from | Memory, or whatever comparison articles it finds | Curated terms, each with a source link and a last-checked date |
| Fine print | Caps, registration and excluded spend often left out | Listed one by one; anything unverified is flagged for you to check |
| Rankings | Many comparison articles are affiliate content | Cardex doesn't rank. Your assistant compares for your spend |
| Local names | May not know what 茶餐廳 or 銀聯 means | 茶餐廳, 匯豐, 銀聯: say it the way you normally would |
FAQ
Will Cardex tell me which card is best?
No. Cardex provides facts like rebate rates, caps and terms. Your AI assistant compares them for your spend and the cards you hold, and tells you which conditions it couldn't verify.
Do I need to give a card number or log in?
No. Cardex takes no card numbers, stores no list of your cards, and sees no transactions. Which cards you hold stays between you and your assistant.
Are the numbers accurate?
Cardex is pre-alpha and every figure today is illustrative, not real issuer terms. Real data goes live card by card after verification, each with a link to the issuer's terms and a last-checked date. Confirm with your issuer before a big spend.
Which AI assistants work with it?
Assistants that support skills or MCP can install it directly, such as Claude and Cursor. Any other assistant that can read a URL and send an HTTP request can follow the method described in the skill.
How is the data updated?
Data is curated ahead of time; nothing is scraped from bank sites on request. Every change is checked against the issuer's page and approved by a person before it goes live.
Do I need to sign up or get an API key?
No. The data connection is public, with no sign-up and no key. The source code is on GitHub under the MIT licence.
Is Cardex affiliated with any card issuer?
No. Cardex is an open-source project with no affiliation, partnership, or endorsement from any issuer. Card and issuer names are used only to describe facts; the issuer's own terms are final.
Set it up by hand
For people who'd rather wire it up themselves. Same two pieces the prompt installs.
The skill
Teaches your assistant what to check before it answers. Save as cardex/SKILL.md in its skills directory.
https://cardex.brandonhk.com/skill.md
The data connection (MCP)
Public, no key needed.
{ "mcpServers": { "cardex": { "url": "https://cardex.brandonhk.com/mcp" } } }