A TCG first: verdicts in your AI

Plug the Ledger into your AI

Others sell raw prices to developers behind sales calls. We put backtested buy/hold/sell verdicts — with a public track record — into Claude, ChatGPT, or any MCP agent, and any member can connect in one click. Straight from our database, cited to the card.

Get your key See Captain pricing

7,000+

products tracked daily

820k+

price points recorded

2.5 yrs

of backtests behind verdicts

100%

of calls graded in public

Get your key

Sign in and open Profile → AI & API, then tap Generate my key. You get a personal connector URL. Included with the Captain tier — no sales form, no waiting.

Add the connector

In Claude: Settings → Connectors → Add custom connector → paste your URL. In ChatGPT and most agent tools: add an MCP server and paste the same URL. That's the whole setup.

Ask the market

Your AI now carries the Ledger with it — live prices, daily verdicts, PSA populations, gem rates, and real sold volume for every card we track.

Things to ask it

“What's the Ledger's verdict on Gear 5 Luffy manga right now?”
“Show me today's biggest One Piece movers and tell me why they're moving.”
“Compare the PSA 10 gem rates of OP09-119 and OP05-119 — which is the safer grade?”
“I'm listing my Shanks alt art this week. What's the price and how many sold in the last 30 days?”

The tools your agent gets

Rate-limited per key (60 calls/min, 5,000/day), tied to your account, revocable in one tap.

search_cardsFind any tracked card or sealed product by name or number — price and verdict attached.

get_cardThe full snapshot: price, momentum, verdict, price band, liquidity tier, PSA pops, gem rate, 30-day sold volume.

get_moversToday's board: the biggest risers or fallers by 7-day momentum, penny-card noise filtered.

For builders

A free card-facts API, no key needed

Every tracked card has a clean JSON endpoint — price, momentum, verdict, pops, gem rate, sold volume. Free and cached, with one condition: attribute “Grand Line Ledger (grandlineledger.com)” wherever the data appears.

GET https://www.grandlineledger.com/api/card/OP09-119?variant=manga

{
  "card":   { "name": "Monkey D. Luffy", "set": "Emperors in the New World", ... },
  "market": { "price_usd": 1234.56, "verdict": "ACCUMULATE",
              "momentum_30d": 0.176, "tcgplayer_sales_30d": 22, ... },
  "psa_population": { "psa10": 1000, "total": 1160, "gem_rate": 86.2 },
  "attribution": "Data by Grand Line Ledger (grandlineledger.com)."
}

OpenAPI 3.0 spec ↓llms.txt for agents ↓

Recommended

Claude & Claude Code

Add the hosted MCP endpoint as a custom connector — no install, always current. Claude discovers the tools automatically and cites every answer back to the card page.

No code

ChatGPT Custom GPTs

Import our OpenAPI spec into GPT Actions and your GPT can pull card facts on demand. Pair it with the MCP endpoint in agent mode for the verdict tools.

Frameworks

LangChain, Vercel AI SDK, agents

Wrap the card-facts endpoint as a typed tool, or speak MCP directly — the connector is standard streamable-HTTP JSON-RPC, so any MCP client library works out of the box.

Universal

Any REST client

The card-facts endpoint is plain JSON over GET. If it can make an HTTP request, it can read the One Piece market — attribution required, that's the whole price.

Prices tell you what a card costs. Verdicts tell you what to do.

Every verdict this API serves comes from mechanical rules backtested on 2.5 years of real prices, and every live call is graded in public at 4 and 8 weeks — inspect the record. That's the difference between a data feed and market intelligence. Data commentary, not financial advice.