Letting an AI agent trade real money is genuinely useful and genuinely risky, and the honest version of the pitch includes both. The good news: the failure modes are knowable, and each has a specific countermeasure. Here are the three that matter, and exactly what stops each.

Failure mode 1 — Runaway behavior

The agent does too much: over-trades, churns the account, chases a strategy past the point of sense, or gets stuck in a loop firing order after order. It’s not malicious — it’s an autonomous system optimizing the wrong thing faster than you can intervene. Robinhood’s own materials warn that AI strategies "may move quickly and be difficult to monitor or stop in real time."

What prevents it:

  • A daily volume cap ceilings total activity no matter how many orders it wants to place.
  • A circuit breaker halts and alerts after N trades in M minutes, catching loops early.
  • The kill switch lets you stop it the moment something looks off. → Building a Kill Switch

Failure mode 2 — Bad instructions

The agent does exactly what you said, not what you meant. A vague prompt ("be aggressive when the market dips") gets interpreted in a way you never intended, and the account pays for the ambiguity. This is the most common real-world failure, and it’s entirely preventable.

What prevents it:

  • An ambiguity rule — the agent halts and asks rather than guessing when intent is unclear.
  • An approval gate on large orders, so a misread instruction can’t execute at size without you.
  • Concentration and per-trade caps that bound the damage of any single interpretation. → Spending & Trade Limits

Failure mode 3 — Manipulated input

The most overlooked one. The agent reads untrusted text — news, tickers, tool output — and an attacker has planted instructions inside it. This is prompt injection, and it’s dangerous precisely because it can target the rules your other guardrails depend on.

What prevents it:

  • An anti-injection rule instructing the agent to refuse and flag any input trying to change its behavior.
  • Hard limits the agent can’t relax through any instruction.
  • The hard kill switch (MCP disconnect) as the backstop a manipulated agent can’t ignore. → Can Your AI Trading Agent Be Hacked?

The pattern: every risk has a guardrail

Notice the structure — none of these are reasons not to use agentic trading. They’re reasons to bound it before you start. Set the three caps, the approval gate, the circuit breaker, the kill switch, and the injection rule, and all three failure modes shrink to a size you chose.

The free SecProve Agent Safety Kit generates every one of those guardrails as a copy-paste config, and the pre-flight checklist makes sure none get skipped.

Two of these three risks are about money. The third is about security — and whether you can spot an attack aimed at your agent is a skill you can measure. Test yours at secprove.com.