Can smart order routing by an AI agent actually get you a better fill?

I read this week that in the first few weeks after Robinhood opened its platform to outside agents, more than 50,000 customers had funded a dedicated agentic trading account and were, in the reporting from Investing.com on 29 June, “trading millions of dollars daily in equities and options.” eToro’s own agent, by the same piece, had already crossed 500,000 trades. The number that stuck with me was smaller and more telling: mentions of AI on the earnings calls of the six brokers covered nearly doubled from the fourth quarter of 2025 to the first quarter of 2026. The agents are here, they are funded, and they are placing real orders.

So the question a lot of us are quietly asking is the practical one. If an agent is now placing my trades, is it getting me a better price than I got clicking the button myself? The honest answer runs through a piece of plumbing most of the excitement skips over entirely.

What a smart order routing system actually decides for a retail order

Start with the phrase itself, because it does a lot of quiet work. A smart order routing system is the software that decides where an order goes once it leaves the app. For an institution splitting a large order across a dozen public venues, that decision is genuinely complex and genuinely the router’s to make. For a retail marketable order at a commission-free broker, the smart order routing system is doing something narrower, and knowing the difference is the whole game.

Most retail marketable orders in the US never touch a public exchange. The router sends them to a wholesaler, a market maker such as Citadel Securities, Virtu, Jane Street, Susquehanna, or Hudson River Trading, that fills the order out of its own inventory. The wholesaler then makes a decision, order by order, that most people assume the router already settled: whether to fill the order right at the best publicly visible price, or a fraction of a cent better, what the industry calls price improvement.

That is the mechanism worth internalizing. The wholesaler improves the price because doing so keeps the broker sending orders its way tomorrow, and it declines to improve when the math on a given name does not support it. So price improvement rises and falls with competition and market conditions, not with how clever the thing that placed the order was.

Why the agentic boom does not change the fill

Here is why this matters right now, with agents suddenly placing a meaningful share of retail orders. The agentic layer being bolted onto brokers changes who decides to trade and when. On Robinhood’s design, as covered when it launched, the agent operates inside a ring-fenced account and “can only access funds explicitly deposited into that account.” That is a sensible containment model. It is not a routing model. Once the agent’s order leaves that account, it enters the same router-to-wholesaler path every manual order takes.

The size of that path is not small. During 2024, wholesalers gave retail customers a combined improvement over public venues that Global Trading pegged in the billions, and the month-to-month swings show how much of a business decision it really is.

Read that gap slowly. The same routing software, the same wholesalers, the same rulebook, and price improvement dropped by roughly 14.5% in a single month because volumes cooled. No agent on the retail side moved that number. It moved because the wholesalers’ own competitive math shifted. An AI agent trading through that layer in August would have received the smaller improvement, and it would have had no lever to pull to change that, because the lever lives inside the wholesaler, not inside the router and certainly not inside the agent.

The agent decides the trade. The wholesaler decides the fill. Confusing the two is how a good tool gets credit for a number it never controlled.

The build-out is racing ahead of this distinction. As LeapRate noted in its survey of the broker rush to wire agents in, “execution-capable MCP integration requires answers to several compliance questions that current regulatory guidance does not yet resolve.” Model Context Protocol, the open standard letting outside AI tools plug into a broker, is the connective tissue here. It is a permission and instruction pipe. It is not an execution venue, and it does not sit between the wholesaler and its price-improvement decision.

Reading the routing before trusting an agent to route on our behalf

So what does a person running real money actually do with this? Not much on the agent, and quite a lot on the broker underneath it. The decision that moves the fills is which broker’s plumbing the agent is standing on, and that is a decision we can inspect in an afternoon.

1. Pull the broker's execution-quality page, not the agent's marketing

   Every major broker publishes price improvement per order and the share of orders filled at or better than the best visible price. That page describes the layer an agent inherits. The agent's own page does not.

2. Separate the routing question from the agent question

   Ask two things independently: is this broker's routing good, and is this agent's decision-making good. A great agent on a mediocre routing stack still gets mediocre fills.

3. Use limit orders where the fill matters

   A marketable order leaves price improvement to the wholesaler's discretion. A limit order sets the worst price we will accept. On thin names, that control is worth more than any routing cleverness.

4. Watch the wholesaler concentration, not the agent brand

   Three wholesalers handle the large majority of retail equity flow. When one firm posts a better share-weighted execution figure than another, that gap is the real edge, and it has nothing to do with which agent placed the order.

5. Size the agent by convenience, not by fill quality

   The honest reason to run an agent is time saved and discipline, not basis points at the fill. Price those benefits, and stop crediting the agent for improvement the wholesaler decides.

The tool-fit call, then, is calm rather than dramatic. An agent can be worth running for what it genuinely gives back, the hours and the emotional distance from our own worst instincts. Just do not buy it for the fill, because the fill was never its to give.

What I keep returning to is that we spent a decade learning to read our own routing disclosures, and the agent era arrived and made a lot of us forget the lesson in a fortnight. The wholesaler’s price-improvement decision did not disappear when the agent showed up. It just moved one more layer away from the person whose money is on the line, and the interesting question is whether any of these agents will ever be allowed close enough to that decision to actually change it.