Pay-per-call arbitrage opportunities between Polymarket and Kalshi prediction markets.
What it does
This x402-gated endpoint returns current arbitrage opportunities between Polymarket and Kalshi, two popular prediction markets. Each call costs up to 0.25 USDC on the Base network and delivers a snapshot of cross-platform pricing discrepancies that may represent profitable trades. The API uses both rule-based matching and LLM-based matching to identify overlapping markets across the two platforms.
The root API listing reveals several endpoints: GET /opportunities (HTML), GET /opportunities/json (JSON), a health check, and internal update/match triggers. The x402 challenge is configured on POST /opportunities, though the root listing advertises GET methods for the payment-gated data. The response MIME type is listed as text/html, suggesting the POST endpoint returns an HTML-formatted view of opportunities. For structured data, the /opportunities/json endpoint may be preferable, though its x402 configuration was not separately probed.
Important caveats from the provider: opportunities do not always exist and results may be empty. Data is informational only — users must verify all calculations independently, as markets move quickly. You are solely responsible for any trading actions taken based on this data.
Capabilities
Use cases
- —Identify mispriced contracts across Polymarket and Kalshi for potential arbitrage trades
- —Monitor prediction market spreads programmatically via agent-initiated paid API calls
- —Build automated trading strategies that consume real-time cross-platform opportunity data
- —Research prediction market efficiency by analyzing pricing discrepancies
Fit
Best for
- —Prediction market traders looking for cross-platform arbitrage
- —Automated trading agents that can pay per call with USDC on Base
- —Researchers studying prediction market pricing efficiency
Not for
- —Users needing historical arbitrage data or backtesting datasets (only current snapshot provided)
- —Anyone expecting guaranteed profitable opportunities (results may be empty)
- —Users who cannot transact with USDC on the Base network
Quick start
curl -X POST https://arb.axryl.com/opportunities \
-H "X-PAYMENT: <x402-payment-header>"Endpoint
Quality
The endpoint is live with a valid 402 challenge and clear pricing (0.25 USDC on Base). However, there is no OpenAPI spec, no documentation beyond the root JSON listing, no output schema, and no example responses. The response MIME type is text/html which is unusual for an API. Several details must be inferred.
Warnings
- —No output schema provided — response format is unknown beyond mimeType text/html
- —No formal API documentation exists (docs, api, pricing, README all return 404)
- —The x402 challenge is on POST /opportunities but the root listing advertises GET /opportunities — method mismatch is unclear
- —Results may be empty; no guarantee of actionable data on any given call
- —Financial data disclaimer: verify all calculations independently; markets move quickly
- —Response mimeType is text/html, not JSON — agents may need to parse HTML or use /opportunities/json instead
Citations
- —The root API lists endpoints including GET /opportunities, GET /opportunities/json, GET /health, POST /update/all, and POST /match/llmhttps://arb.axryl.com
- —The x402 challenge requires up to 250000 units (0.25 USDC) on the Base network, paid to 0xb1e82E1f0d3a736Fe662269Adc10FBe460fE1Bf9https://arb.axryl.com/opportunities
- —The provider disclaims that opportunities do not always exist and results may be empty, and data is for informational purposes onlyhttps://arb.axryl.com/opportunities