Similar Markets API — Semantic Market Search
The /similar-markets endpoint embeds arbitrary text and finds the closest resolved prediction markets using a pgvector HNSW index. Returns historically similar markets with their outcomes.
Endpoint
GET /api/feeds/similar-markets?q=Will+Bitcoin+hit+100k&limit=10Parameters
| Param | Type | Required | Description |
|---|---|---|---|
q | query | Yes | Text to search (market question, scenario, event) |
limit | query | No | Max results (default: 10, max: 50) |
Pricing
$0.005 per request (upfront payment).
Example response (truncated)
{
"query": "Will Bitcoin hit 100k",
"markets": [
{
"market_key": "btc-100k-2024",
"question": "Will Bitcoin reach $100,000 by end of 2024?",
"similarity": 0.89,
"outcome": "no",
"resolved_at": "2024-12-31T23:59:59Z",
"category": "crypto"
},
{
"market_key": "btc-ath-2021",
"question": "Will Bitcoin surpass its all-time high in 2021?",
"similarity": 0.82,
"outcome": "yes",
"resolved_at": "2021-11-10T00:00:00Z",
"category": "crypto"
}
]
}Use cases
Historical Analogs
"Will Bitcoin hit $100k?" — find the 5 closest resolved markets with 0.89+ similarity. See what happened: 4 resolved "no", 1 resolved "yes". The base rate is 80% no. Use that as your prior.
Backtest Your Thesis
Query "Bitcoin ETF approval rally" and get 12 similar past events. 8 played out as expected, 4 didn't. Know the odds before you commit capital. $0.005 per search.
Ground Agent Forecasts
Before your AI agent votes "yes" on a market, search for similar resolved markets. If 70% of analogs resolved "no", the agent should lower its confidence. Embeddings capture semantic similarity, not just keywords.
"What Happened Last Time?"
A black swan event just hit. Search for similar past events and see the outcome distribution: median drawdown was -8%, but p05 was -22%. Size your hedge for the tail, not the median.
Frequently asked questions
How do I find historically similar crypto prediction markets?
GET /api/feeds/similar-markets?q=Will+Bitcoin+hit+100k. The endpoint embeds your query text and finds the closest resolved prediction markets via a pgvector HNSW index, returning similarity scores and outcomes.What is semantic similar market search?
How much does the similar markets API cost?
$0.005 per request (upfront payment). Pay with USDC on Solana or Base via x402. Use /outcome-stats at $0.01 for aggregated YES/NO distributions across similar markets.