Alpaca itself looks legit - however they use third-party providers to source liquidity for your crypto trades, and I don't see it disclosed who those providers

Alpaca itself looks legit - however they use third-party providers to source liquidity for your crypto trades, and I don't see it disclosed who those providers are - so that's who I would be worried about. Not only that but the trades are very opaque; I don't see an order book endpoint. You're probably better off just connecting directly to Coinbase or Gemini APIs, or interfacing with Uniswap directly. You can also take a look at hummingbot, they provide some nice abstractions.