Polygon.io API
Financial market data platform providing real-time and historical stock, options, forex, and crypto data via REST and WebSocket APIs with comprehensive coverage of US markets.
Score Breakdown
⚙ Agent Friendliness
🔒 Security
API key auth. Financial market data. SOC2 not documented. Rate limits by plan tier. Market data is not PII but usage must comply with data vendor agreements.
⚡ Reliability
Best When
An agent needs comprehensive US financial market data - stocks, options, crypto - for analysis or algorithmic trading signals.
Avoid When
You need order execution (use Alpaca) or primarily need international market data.
Use Cases
- • Fetching OHLCV (candlestick) data for backtesting trading strategies
- • Real-time stock quotes and trade streaming via WebSocket
- • Options chain data for derivatives analysis agents
- • Technical indicator data for signal generation
- • Ticker search and company fundamentals lookup
Not For
- • Order execution (data only, not a broker)
- • International markets outside US (limited non-US coverage)
- • Teams needing free real-time data at scale
Interface
Authentication
API key in query parameter or Authorization header. Single key for all endpoints. Very agent-friendly.
Pricing
Free tier is quite limited (delayed data, rate limited). Real-time data requires paid plan. Pricing is reasonable for indie developers and algo traders.
Agent Metadata
Known Gotchas
- ⚠ Free tier rate limits (5/minute) make it almost unusable for agents - paid plan needed
- ⚠ Real-time vs delayed data access depends on plan level
- ⚠ Ticker symbols must be exact (e.g., AAPL not Apple)
- ⚠ Options data uses OCC symbology which requires understanding of the format
- ⚠ WebSocket streams require reconnection logic - connections drop periodically
Alternatives
Full Evaluation Report
Detailed scoring breakdown, competitive positioning, security analysis, and improvement recommendations for Polygon.io API.
Scores are editorial opinions as of 2026-03-06.