Public's Agentic Brokerage: using AI to invest on Public

Public's AI Agents page (checked October 2026) calls the company "the world's first Agentic Brokerage", a claim that is Public's own. The legal definition is more useful. Public's Agentic Brokerage Agreement describes it as a conversational AI tool that lets you enter instructions for "self-directed, recurring transactions" in your account, where a transaction can be a trade order, a money transfer, an alert or another account action.

In practice it works like this. You type what you want in a chat box. The AI asks follow-up questions if your instruction is vague, then turns it into one or more confirmation screens. You review and confirm. From then on, the set of instructions (Public calls it an Agent) runs automatically, on a schedule or whenever its conditions come true, until you or Public pause or end it.

That last point is the one to understand before using it. Public's agreement states that once an Agent is active, Public will not alert you before each transaction or wait for your confirmation, and that executed transactions cannot be cancelled or reversed. The approval happens once, at setup. After that, the Agent acts on the rule you approved.

According to Public's AI Agents page and its help article "Agents: The Basics" (updated June 9, 2026), Agents can:

• Trade across asset classes: Public says Agents support trading in stocks, options and crypto.
• Run on triggers: an Agent runs when the conditions you set come true, such as a price move, a market event, a portfolio change or a recurring schedule.
• Move and manage cash: Public describes automating "everything from trading strategies to money movement".
• Use market data: Public says Agents can access 30 years of earnings, financials and price data, plus real-time information.

The limits, from the same sources: Agents are rolling out to Public's waitlist, the workflows are web only for now with mobile "coming soon", and Public notes that certain listed capabilities are not available yet. Public also states plainly that Agents are not financial advisors and do not recommend trades. The agreement adds that you are solely responsible for whether a strategy suits you, and for watching your active Agents and acting quickly if one does something you did not intend.

Public has two other AI products worth separating from Agents. Generated Assets are custom indices you describe in a prompt; Public's help article (updated November 18, 2025) says AI screens stocks against your criteria and shows how the index would have compared with the S&P 500. They are an advisory product, and Public's fee schedule lists a 0.49% annual management fee for Generated Assets accounts. Alpha is described on public.com as an experimental AI research tool that may produce inaccurate responses.

Separate from its own Agents, Public runs an MCP server. MCP (Model Context Protocol) is the open standard many AI assistants use to talk to outside services. Public's MCP page (checked October 2026) says it works with Claude, Perplexity and ChatGPT, and its hosted setup docs add Claude Code, Codex, Grok and Meta Muse.

There are two ways to connect:

• Hosted: you add https://mcp.public.com/mcp as a connector in your assistant and sign in to Public in your browser (OAuth). This is the simpler route for Claude, ChatGPT, Perplexity and Grok.
• Local, for Claude Desktop: you install a small program on your computer and paste a Public API key and account ID into Claude Desktop's config file. Public's guide (updated August 20, 2026) says the key is generated in Account Settings, Security, API.

Once connected, Public says an assistant can answer questions about your holdings, performance, sector exposure and P&L, screen stocks, build watchlists, and place trades. Its MCP page lists US-listed stocks, ETFs, options, crypto and bonds, and its Claude guide lists market, limit, stop and stop-limit orders and fractional orders by dollar amount. Access is limited to US securities markets.

Public's own warnings belong next to that list. Its MCP page says "trades may be executed by your AI agent without your direct input on each transaction", that you assume all risk for those trades, and that Public does not control, supervise, monitor or audit any third-party AI agent. Its setup docs say every order placed through an MCP client is a real order with real money, and its Claude guide says there is no paper trading mode. Public recommends opening a dedicated account for automated strategies and AI trading, so a mistake is limited to the money in that account. For step-by-step setup, see our guides to connecting Claude to Public and connecting ChatGPT to Public.

Public's fee schedule (October 2026 edition) lists $0 commissions on US-listed stocks and ETFs, in regular and extended hours, and $0 on stock and ETF options. Index options are $0.35 per contract, and small regulatory and exchange fees are passed through, mostly on sells. Public's MCP page says MCP access itself is included with a brokerage account at no extra cost. Whatever your AI assistant charges is separate: Public's Claude guide notes a paid Claude plan may be needed for MCP connectors.

The rule that affects investing most is the fractional minimum. Public's Fractional Shares Trading Disclosure (August 2026) says Public will not accept a fractional order under $5 outside an Investment Plan, or under $1 inside one. Public's help center gives the same $5 figure for fractional stock buys. Investment Plans are Public's own recurring-buy feature; orders placed by an outside app, Walnut included, are ordinary orders, so the $5 floor applies to each one.

For a single stock that hardly matters. For a basket, where one dollar amount is split across several stocks, it matters a lot, because the smallest weight sets the floor. The arithmetic is simple: divide $5 by the smallest weight.

• Smallest weight 25%: $5 / 0.25 = $20 per buy
• Smallest weight 20%: $5 / 0.20 = $25 per buy
• Smallest weight 10%: $5 / 0.10 = $50 per buy
• Smallest weight 5%: $5 / 0.05 = $100 per buy

Below that amount, the smallest leg falls under $5 and Public rejects it, so the basket ends up bought only in part.

Walnut is an AI investing app built around baskets: a set of stocks or ETFs with a target weight for each. It reads your Public holdings so the assistant can talk about what you actually own, and it places the buys you approve. Here is the flow.

1. Connect Public

Open the Brokerage page in Walnut and choose Public, or ask the Walnut assistant to connect it. A secure sign-in opens in its own tab, and you log in to Public there. Walnut never sees your Public password, and there is no API key, config file or MCP link to set up.

2. Fund the account in Public

Move cash into your Public account in the Public app. Walnut does not move money at any point. If you follow Public's suggestion of a dedicated account for AI trading, connect that one.

3. Build or pick a basket

Set your own weights ("AI chips: NVDA 30%, AVGO 25%, TSM 25%, AMD 20%"), ask the assistant to draft a basket around a theme, or start from one of Walnut's ready-made ideas and adjust it.

4. Approve the buy

Open the basket's Invest dialog and enter a dollar amount. Orders go in as dollar amounts, so each buy lands on whatever fraction of a share it covers. Walnut shows each order before anything is sent, and nothing is placed until you approve. Orders are market buys for the day. One placed outside market hours waits as pending until Public fills it, and Walnut counts it only once the fill is confirmed.

5. Optionally, make it recurring

In the same dialog, choose Recurring instead of One-time and pick weekly, every two weeks or monthly. You approve the plan once. On each date Walnut spends the fixed amount across the weights using cash already in your Public account. It reads the account's cash balance rather than its margin buying power, so a contribution is sized to cash you hold. If the cash is not there, the run is skipped and retried for up to five days, and a notification tells you. Walnut also warns at setup when the smallest weight would produce an order under Public's $5 minimum.

What Walnut does not do on Public: sell, trade options or trade crypto. Those stay in the Public app, or with Public's own Agents or MCP if you use them.

Say you have $200 in your Public account and a basket with NVDA 30%, AVGO 25%, TSM 25% and AMD 20%. You open Invest, choose One-time, and enter $200. Walnut works out the split:

• NVDA: 30% of $200 = $60
• AVGO: 25% of $200 = $50
• TSM: 25% of $200 = $50
• AMD: 20% of $200 = $40

You approve four dollar-amount market buys. Every leg is well above $5, so all four go through, each buying whatever fraction of a share the amount covers at the fill price.

Now make it recurring at $40 a month. Each run places $12 in NVDA, $10 each in AVGO and TSM, and $8 in AMD. All clear $5. Drop the plan to $20 a month and the split becomes $6, $5, $5 and $4: the AMD leg is under $5, so Public would reject it. Walnut flags this when you set the plan up and names the amount that works, $25 here (from $5 / 0.20).

Afterwards the assistant can tell you how the basket is doing and read it next to the rest of your Public holdings. That matters if you already own some of the same chip stocks outside the basket.

The three routes overlap but are built for different work.

• Public's Agents suit conditional automation inside Public: rules that trigger on prices, events or schedules, across stocks, options and crypto, plus cash moves. They are on a waitlist and web only for now. Once active, they act without asking again.
• ChatGPT or Claude with Public's MCP suit open-ended research and one-off trades of almost any kind, with the most flexibility and the most need to write your own limits.
• Walnut suits investing to a plan: a basket with fixed weights, one dollar amount split across it, every one-time buy approved, and an optional recurring buy approved once. It covers buys of US stocks and ETFs only.

They are not exclusive. Many people research in a general assistant and invest through a tool that keeps the plan in one place.

• Treating one approval as ongoing review. A Public Agent, or an MCP assistant told to act freely, keeps trading after you approve the rule. Check completed trades regularly.
• Connecting your main account. Public itself suggests a dedicated account for AI trading. Size it to what you are comfortable letting software act on.
• Small amounts across many stocks. Ten stocks at 10% each need $50 per buy on Public. A $30 plan leaves every leg under $5.
• Reading AI output as advice. Public's agreement says its Agentic Brokerage gives no recommendations, and Walnut is not an investment adviser either. The tools carry out decisions; the decision stays yours.

All checked October 16, 2026: Public's AI Agents page; the Agentic Brokerage Agreement; Agents: The Basics (updated June 9, 2026); the Public MCP Server page; the hosted MCP setup docs; How to Trade Stocks, Options & Crypto Using Claude (updated August 20, 2026); the Public fee schedule; the Fractional Shares Trading Disclosure; What is the minimum amount to invest in stock?; and What is Generated Assets? Walnut is not affiliated with Public, is not a broker or an investment adviser, and this guide is educational, not personalized investment advice. For the Robinhood equivalent, see Robinhood agentic trading.