the402 endpoint detail

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graphadvocate.com kalshi-polymarket spread

https://graphadvocate.com/kalshi-polymarket/spread

answers 402

Cross-source arbitrage spread between Kalshi and Polymarket on a topic. POST {topic, limit?}. Pulls matching markets from both venues (Politics + Elections overlap heavily), computes price mid-spread + arbitrage direction. JOIN that single-source passthrough APIs (incl. Pinax Token API) structurally can't return — this is what survives Pinax shipping Kalshi support later.

We sent a real POST request to this endpoint and it answered 402 with payment requirements we could parse.
Price
$0.05
Network
base
Pay to
0x0FF5A6ecef783BBA35463ec2F8403B9B5e9e7C86
Spec dialect
v2 (declares x402Version 2)
Transport
PAYMENT-REQUIRED header
HTTP method
POST
Response latency
192 ms
Payment options
1 usable of 1
Last checked
2026-08-15T14:30:55.154Z (1h ago)
Category
finance-crypto

Re-check it yourself:
curl "https://api.the402.dev/validate?url=https%3A%2F%2Fgraphadvocate.com%2Fkalshi-polymarket%2Fspread"