Prediction Market APIs Compared

import httpx
import time
import base64
from cryptography.hazmat.primitives import hashes, serialization
from cryptography.hazmat.primitives.asymmetric import padding

# Load your RSA private key
with open("kalshi_private_key.pem", "rb") as f:
    private_key = serialization.load_pem_private_key(f.read(), password=None)

timestamp = str(int(time.time() * 1000))
method = "GET"
path = "/trade-api/v2/markets"

# Sign: timestamp + method + path
message = f"{timestamp}{method}{path}".encode()
signature = private_key.sign(
    message,
    padding.PSS(mgf=padding.MGF1(hashes.SHA256()), salt_length=padding.PSS.MAX_LENGTH),
    hashes.SHA256(),
)

resp = httpx.get(
    f"https://trading-api.kalshi.com{path}",
    params={"limit": 5},
    headers={
        "KALSHI-ACCESS-KEY": "your-api-key-id",
        "KALSHI-ACCESS-SIGNATURE": base64.b64encode(signature).decode(),
        "KALSHI-ACCESS-TIMESTAMP": timestamp,
    },
)
markets = resp.json()["markets"]
for m in markets:
    print(f"{m['ticker']} | {m['title']} | YES: ${m['yes_bid'] / 100:.2f}")

import httpx

# No auth needed for market discovery
resp = httpx.get(
    "https://gamma-api.polymarket.com/markets",
    params={"limit": 5, "active": True, "order": "volume24hr", "ascending": False},
)
markets = resp.json()
for m in markets:
    question = m["question"]
    volume = float(m.get("volume", 0))
    print(f"{question} | Volume: ${volume:,.0f}")

import httpx

# Robinhood event data (read-only, requires OAuth token)
# Note: programmatic trading is not publicly available
resp = httpx.get(
    "https://api.robinhood.com/events/",
    headers={"Authorization": "Bearer YOUR_ROBINHOOD_TOKEN"},
    params={"limit": 5},
)
events = resp.json()["results"]
for e in events:
    print(f"{e['slug']} | {e['title']}")

import httpx
import time
import base64
from cryptography.hazmat.primitives import hashes, serialization
from cryptography.hazmat.primitives.asymmetric import padding

# --- Kalshi (RSA-PSS signed requests) ---
with open("kalshi_private_key.pem", "rb") as f:
    kalshi_key = serialization.load_pem_private_key(f.read(), password=None)

ts = str(int(time.time() * 1000))
msg = f"{ts}GET/trade-api/v2/markets".encode()
sig = kalshi_key.sign(
    msg,
    padding.PSS(mgf=padding.MGF1(hashes.SHA256()), salt_length=padding.PSS.MAX_LENGTH),
    hashes.SHA256(),
)
kalshi_markets = httpx.get(
    "https://trading-api.kalshi.com/trade-api/v2/markets",
    params={"limit": 20},
    headers={
        "KALSHI-ACCESS-KEY": "your-kalshi-key",
        "KALSHI-ACCESS-SIGNATURE": base64.b64encode(sig).decode(),
        "KALSHI-ACCESS-TIMESTAMP": ts,
    },
).json()["markets"]

# --- Polymarket (separate Gamma API, different data shape) ---
poly_markets = httpx.get(
    "https://gamma-api.polymarket.com/markets",
    params={"limit": 20, "active": True},
).json()

# --- Robinhood (OAuth, different structure entirely) ---
rh_events = httpx.get(
    "https://api.robinhood.com/events/",
    headers={"Authorization": "Bearer your-robinhood-token"},
    params={"limit": 20},
).json()["results"]

# --- Now normalize all three into a common format ---
combined = []
for m in kalshi_markets:
    combined.append({
        "platform": "kalshi",
        "title": m["title"],
        "yes_price": m["yes_bid"] / 100,
        "volume": m.get("volume", 0),
        "id": m["ticker"],
    })
for m in poly_markets:
    combined.append({
        "platform": "polymarket",
        "title": m["question"],
        "yes_price": float(m.get("outcomePrices", "[0.5]").strip("[]").split(",")[0]),
        "volume": float(m.get("volume", 0)),
        "id": m["conditionId"],
    })
for e in rh_events:
    combined.append({
        "platform": "robinhood",
        "title": e["title"],
        "yes_price": None,  # Requires additional API call per event
        "volume": None,
        "id": e["slug"],
    })

# Sort by volume (where available)
combined.sort(key=lambda x: x.get("volume") or 0, reverse=True)
for m in combined[:10]:
    print(f"{m['platform']:12} | {m['title'][:50]:50} | YES: {m['yes_price']}")

{
  "platform": "kalshi",
  "market_id": "KXFED-26MAR19",
  "title": "Will the Fed cut rates at the March 2026 meeting?",
  "url": "https://kalshi.com/markets/kxfed-26mar19",
  "category": "economics",
  "yes_price": 0.62,
  "volume_24h": 48250.00,
  "liquidity": 125000.00,
  "open_interest": 340000.00,
  "resolution_date": "2026-03-19T18:00:00Z",
  "updated_at": "2026-03-24T14:30:00Z"
}

# Kalshi only
curl "https://api.rekko.ai/v1/markets?source=kalshi&limit=20" \
  -H "Authorization: Bearer YOUR_API_KEY"

# Polymarket only
curl "https://api.rekko.ai/v1/markets?source=polymarket&limit=20" \
  -H "Authorization: Bearer YOUR_API_KEY"