Alpaca Trading API
Alpaca is a commission-free stock and cryptocurrency trading API designed for developers and algorithmic traders. It supports market, limit, and stop orders, portfolio management, real-time market data streaming via WebSocket, and paper trading for strategy testing without real money.
Score Breakdown
⚙ Agent Friendliness
🔒 Security
API key + secret key pair. Paper trading sandbox. FINRA-regulated broker-dealer. SOC2. CRITICAL: Production API executes real trades. Always use paper trading until thoroughly tested and validated.
⚡ Reliability
Best When
An agent needs to execute US equity or crypto trades programmatically, especially for algorithmic strategies or automated portfolio management.
Avoid When
Sub-millisecond execution latency is required, institutional-grade clearing is needed, or trading instruments beyond US stocks and crypto.
Use Cases
- • Building algorithmic trading bots and automated trading strategies
- • Paper trading for testing trading agents before going live
- • Portfolio rebalancing automation
- • Real-time market data ingestion and analysis
- • Options and crypto trading automation
- • Fractional share trading for micro-investment apps
Not For
- • Institutional or high-frequency trading (not built for sub-millisecond execution)
- • International users outside the US (primarily US-based brokerage)
- • Trading futures, forex, or commodities (equities and crypto only)
Interface
Authentication
API Key ID and API Secret Key pair, generated in the Alpaca dashboard. Separate key pairs for paper and live trading environments. Keys are per-account. No OAuth or fine-grained scopes — a key grants full account access. OAuth2 available for broker-dealer API (multi-account).
Pricing
The trading API itself has no subscription fee. Revenue comes from payment for order flow, crypto spreads, and premium market data. Paper trading is an excellent free sandbox for agent development.
Agent Metadata
Known Gotchas
- ⚠ Paper and live trading environments use different base URLs and key pairs — easy to accidentally use live keys in testing
- ⚠ Market hours matter — orders submitted outside market hours behave differently (held, rejected, or extended-hours depending on flags)
- ⚠ Order fills are asynchronous — agents must poll order status or stream updates via WebSocket
- ⚠ Pattern Day Trader (PDT) rule applies — less than $25k account triggers restrictions on day trades
- ⚠ Fractional shares cannot be used with all order types
- ⚠ Crypto trading fees apply unlike equity trading — agents tracking P&L must account for spread
- ⚠ Free market data tier has 15-minute delay — real-time data requires a paid subscription
- ⚠ Rate limits (200 req/min) are easy to hit in tight agent loops — implement backoff
Alternatives
Full Evaluation Report
Detailed scoring breakdown, competitive positioning, security analysis, and improvement recommendations for Alpaca Trading API.
Scores are editorial opinions as of 2026-03-06.