Official venue APIsAPIfree
Opinion Open API: what it exposes, how it authenticates, where it stops
Last checked 2026-09-08
Opinion Labs runs OPINION prediction markets on BNB Chain (chain ID 56) and publishes three developer surfaces: the Opinion Open API (REST, OpenAPI 3.0), the Opinion WebSocket (read-only streaming) and the Opinion CLOB Python SDK for order placement. One API key works across all three.
It is for developers who want market data over plain HTTP and are willing to place orders through the Python SDK rather than a raw REST call.
What the API exposes
The Open API groups endpoints into market, token, quote token, position, trade, order, resolution and auth. Public endpoints return market metadata, volumes, latest and historical prices, order book depth and the list of quote currencies without a key; authenticated endpoints need one.
The WebSocket streams price ticks, trades, order book deltas, market activation and resolution events, and aggregated metrics. It is read-only by design; trading operations go through the CLOB SDK, which also splits, merges and redeems tokens on chain.
The Python SDK (pip install opinion_clob_sdk, GitHub opinion-labs/opinion-clob-sdk) is labelled a Technical Preview at version 0.4.1 and points at host https://proxy.opinion.trade:8443 with chain_id 56.
Authentication and rate limits
Send the key in an apikey header. Create one by signing an EIP-712 message (domain Opinion OpenAPI, version 1, chainId 56) and calling POST /auth/api-key with OPINION_ADDRESS, OPINION_SIGNATURE and OPINION_TIMESTAMP headers; GET and DELETE on the same route use their own action strings. Signatures expire after 5 minutes, each wallet holds one active key, and the wallet must already be onboarded on opinion.trade. An application form remains as an alternative route.
The rate limit is 15 requests per second per API key. Higher limits are handled by email to Opinion Labs.
Pricing and access
No API fee. Trading fees apply to takers only and range from 0% to 1%, rising as probability approaches 50%, with a $5 minimum order and a $0.25 minimum fee. Discounts stack to 100% of the curve fee, though the $0.25 floor still applies. Fees are denominated in the settlement asset, such as USDT.
Where it falls short
15 requests per second is tight for anything that scans many markets, and the WebSocket cannot place orders.
Order entry is Python-only through a preview-labelled SDK; TypeScript users have no official path.
The $0.25 minimum fee dominates small tickets, and mainnet is the only documented chain.
Who should use it
Python builders on BNB Chain who want self-serve keys and a fee schedule that favours makers.
Latency-sensitive strategies should weigh the per-second limit before committing.
Questions about Opinion Open API
How do I get an Opinion API key?
Sign an EIP-712 message with an onboarded wallet and POST it to /auth/api-key; the key is issued instantly. A Google application form is the alternative.
What is the Opinion API rate limit?
15 requests per second per API key. Contact Opinion Labs for more.
Can I place orders through the Opinion WebSocket?
No. The WebSocket is read-only. Orders go through the Opinion CLOB Python SDK.
What are Opinion trading fees?
Takers pay 0% to 1% depending on price, with a $5 minimum order and $0.25 minimum fee. Makers pay nothing.
Official APIs for building. One book for trading.
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