Alpaca vs Marcus Invest: Which Is Better in 2026?

Prices checked October 2026. A price marked (Oct 2026) was read on the vendor's own pricing page; others are described without a number because we could not verify one.

A developer-first brokerage with an official MCP server for real-time data, paper trading, and execution by AI agents. Best for people who code.

How it works: Alpaca is a brokerage you talk to through code: a REST and websocket API exposes market data, paper trading, and live commission-free execution, and its official MCP server lets an AI agent pull data, test in a paper account, and place real orders programmatically. You build against that API (or wire up an agent to it); there are no buttons to tap in an app.

In practice, Alpaca’s AI official MCP server (data + execution). It is a brokerage API for people building their own AI agent, best suited to developers building AI agents. On connecting an account: alpaca accounts. On execution: read + trade + paper. Cost: free (open source).

One real limitation: Developer-first; requires code and self-hosting.

Goldman Sachs' former automated investing service, closed in 2024 when its accounts moved to Betterment.

How it works: Marcus Invest used a questionnaire to set a risk level and invested in model ETF portfolios built by Goldman Sachs. Goldman Sachs closed it in 2024 and transferred the accounts to Betterment, so anyone who held one now has a Betterment account under Betterment's own pricing.

In practice, Marcus Invest’s AI discontinued in 2024. It is a robo-advisor (hands-off automated investing), best suited to former Marcus Invest clients checking where their account went. On connecting an account: no (holds your money at Marcus). On execution: not offered. Cost: discontinued; accounts moved to Betterment (2024).

One real limitation: Marcus Invest is closed: Goldman Sachs moved its accounts to Betterment in 2024, so the comparison that matters now is Betterment itself.

Category comes first. Alpaca focuses on developers building AI agents (official MCP server (data + execution)), and Marcus Invest on former Marcus Invest clients checking where their account went (discontinued in 2024). On broker connection they differ too: Alpaca is “Alpaca accounts” versus Marcus Invest at “No (holds your money at Marcus)”. That shapes everything downstream: how personal the answers are, where trades settle, and how much control you keep over individual positions.

Every tool gives something up for what it does well. Below is the give-and-take on each, so you can weigh the specific strengths against the limitations that come with them, beyond the headline category.

For AI investing tools, the distinction that matters most is whether the tool works from your actual, connected positions or reasons from something else: a separate account it manages for you, or the tickers and numbers you feed it. It decides how personal the answers can be, and where your money physically lives.

• Alpaca: connects specific supported accounts. Alpaca connects a defined set of accounts (Alpaca accounts), so whether it can see your holdings depends on whether your money is at one of them.
• Marcus Invest: manages a separate account it holds. Marcus Invest does not read the brokerage you already use. It opens and holds a new account, then invests the money you move into it, so its view is limited to what sits inside Marcus Invest.

This is where they diverge most. One works from your real, connected account while the other does not, so if you want an assistant grounded in the exact positions you already hold, that gap is the thing to weigh first. This holdings-aware angle is the one Walnut is built around: it connects the brokerage you already use and reasons from your live positions, read-only by default, with any trades left for you to approve.

Each one wins a different job, so the answer depends on which job you need done.

• Choose Alpaca if you want developers building AI agents. Its AI official MCP server (data + execution), and it costs free (open source). It is built for developers building their own automated or AI-driven trading systems. Keep in mind: developer-first; requires code and self-hosting.
• Choose Marcus Invest if you want former Marcus Invest clients checking where their account went. Its AI discontinued in 2024, and it costs discontinued; accounts moved to Betterment (2024). It is built for nobody opening a new account, since the service is closed; former clients should compare Betterment, where their account now sits. Keep in mind: marcus Invest is closed: Goldman Sachs moved its accounts to Betterment in 2024, so the comparison that matters now is Betterment itself.
• Choose Walnut if you want a keep, trim or exit read on the stocks you already own, and placing the trades you approve. It is an AI investing app that connects the broker you already use, and it costs free; Walnut Plus $9.99/mo on the web; no fee on assets.

Because they sit in different categories, this is not strictly either-or: some investors use one for developers building AI agents and the other for former Marcus Invest clients checking where their account went, and watch for overlapping costs.

Cost is easy to misread when two tools charge in different shapes, so compare the model, not just the number. Alpaca: free (open source). Marcus Invest: discontinued; accounts moved to Betterment (2024). A percentage-of-assets fee scales with your balance, a flat subscription does not, and a “free” tier usually earns elsewhere (on cash, order flow, or premium upgrades), so the cheapest headline is not always the cheapest outcome for your situation.

Prices checked October 2026. Pricing and tiers change, so confirm the current numbers on each provider’s own site before you decide.

Walnut is an AI investing app, and it is the pick for a keep, trim or exit read on the stocks you already own, and placing the trades you approve (free; Walnut Plus $9.99/mo on the web; no fee on assets). It connects the brokerage you already use, read-only by default, gives each holding a keep, trim or exit read against the S&P 500, flags any position above a quarter of the portfolio, and places the trades you approve. You use it through its own assistant, or inside Claude or ChatGPT. See Walnut vs Alpaca and Walnut vs Marcus Invest.