Prices & Orderbook

Openfish uses a central limit order book for prediction market trading. Prices are not set by the platform; they emerge from buy and sell orders placed by users, agents, and market makers.

In the current FISH/off-chain deployment, matched trades update the Openfish ledger.

Prices Are Probabilities

Outcome share prices range from ♓︎0.00 to ♓︎1.00. A price can be read as the market’s implied probability for that outcome.

Price	Implied probability
♓︎0.25	25%
♓︎0.50	50%
♓︎0.75	75%

Example:

Best Yes bid = ♓︎0.34
Best Yes ask = ♓︎0.40
Displayed midpoint = ♓︎0.37

The midpoint is a reference. A buyer crossing the spread pays the ask; a seller crossing the spread receives the bid.

Order Book Structure

Each outcome token_id has an order book:

OrderBook
  Bids: buy orders sorted by price descending, then time
  Asks: sell orders sorted by price ascending, then time

The engine applies price-time priority:

Better price fills first.
Earlier order fills first when prices are equal.

Core Price Endpoints

These endpoints read the current in-memory CLOB order book at request time. They are the right REST source for current token-level prices.

Best bid/ask:

curl "https://api.openfish.me/price?token_id=YOUR_TOKEN_ID"

Midpoint:

curl "https://api.openfish.me/midpoint?token_id=YOUR_TOKEN_ID"

Spread:

curl "https://api.openfish.me/spread?token_id=YOUR_TOKEN_ID"

Batch queries:

curl -X POST "https://api.openfish.me/midpoints" \
  -H "Content-Type: application/json" \
  -d '["token_id_1", "token_id_2"]'

curl -X POST "https://api.openfish.me/spreads" \
  -H "Content-Type: application/json" \
  -d '["token_id_1", "token_id_2"]'

Book Depth

Retrieve aggregated resting liquidity:

curl "https://api.openfish.me/book?token_id=YOUR_TOKEN_ID"

Example response:

{
  "bids": [
    { "price": "0.55", "size": "150" },
    { "price": "0.54", "size": "200" }
  ],
  "asks": [
    { "price": "0.58", "size": "100" },
    { "price": "0.60", "size": "300" }
  ]
}

Large orders can sweep multiple levels and receive a worse average fill price. Check book depth before submitting size.

Tick Sizes

Markets define the minimum allowed price increment.

Tick size	Example prices
`0.01`	`0.01`, `0.02`, `0.99`
`0.001`	`0.001`, `0.002`, `0.999`
`0.0001`	`0.0001`, `0.0002`, `0.9999`

Orders that do not align with the market’s tick size are rejected.

curl "https://api.openfish.me/tick-size?token_id=YOUR_TOKEN_ID"

Trade Execution

When a buy and sell order match:

The buyer receives outcome shares.
The seller receives FISH.
The ledger records balance movements.
Fees and rebates are recorded according to market configuration.
Order and trade statuses update.

This is the normal execution model for the current openfish.me deployment.

Price History

The CLOB records price snapshots for active markets. History endpoints are market-level and use condition_id, not token ID. In production, snapshots are written every 300 seconds.

curl "https://api.openfish.me/prices-history?market=YOUR_CONDITION_ID"

curl -X POST "https://api.openfish.me/batch-prices-history" \
  -H "Content-Type: application/json" \
  -d '[{"market":"condition_id_1","fidelity":50},{"market":"condition_id_2","fidelity":50}]'

Use /price, /prices, /book, or /books when you need the latest in-memory order book state. Use /ws/market when you need event-driven updates after your initial REST snapshot.

Persistence And Recovery

The live order book is held in memory for speed. Orders are also stored in PostgreSQL, allowing the CLOB server to rebuild books from LIVE orders after restart.

During normal operation, database records provide the durable source for recovery, analytics, and audit trails.