Your trading agent still thinks the PDT rule exists

#mcp #ai #trading #agents

Ask most LLMs about day trading and they will tell you about the Pattern Day Trader rule: four day trades in five business days, and you need $25,000 in the account.

That rule is gone. FINRA Regulatory Notice 26-10 replaced it on June 4, 2026 with an intraday margin standard. A margin account now builds an intraday margin deficit when it buys or sells short. The trader must meet that deficit promptly. Leaving deficits unmet past the 5th business day as a practice triggers a 90-day restriction. Brokers may keep the old PDT rule until October 20, 2027, so your agent also needs to know which regime its broker uses.

This matters if you run an agent against a real broker. An agent that believes the old rule will refuse trades it could make. An agent that ignores both rules will get its account restricted.

Check the current rules from your agent

I built a small service that returns the current rules with effective dates and sources. The rules endpoint is free:

curl -X POST https://agent-financial-advisor.agent-financial-advisor.workers.dev/v1/tools/rules_digest \
  -H "content-type: application/json" -d '{}'

Check an order before you send it

The pre_trade_check tool runs an order past a compliance and risk review. It checks buying power, settlement violations, intraday margin, Reg SHO, wash sales, concentration and fat-finger prices. It returns approve, approve_with_warnings or reject, with reasons.

Size a position

curl -X POST https://agent-financial-advisor.agent-financial-advisor.workers.dev/v1/tools/position_size \
  -H "content-type: application/json" \
  -d '{"equity":50000,"entry_price":100,"stop_price":95,"method":"fixed_fractional"}'

That call sizes a position to risk 1% of equity to the stop: 100 shares, $500 at risk.

Use it as an MCP server

Point any MCP client at https://agent-financial-advisor.agent-financial-advisor.workers.dev/mcp. The agent sees 8 tools, including position sizing, tax-lot planning and a backtest audit that computes the Deflated Sharpe Ratio.

Pricing

The rules digest is free. Each IP gets 5 free calls a day, and a free API key gets 25. After that, calls cost 1 to 10 cents in USDC via the x402 protocol, so an agent can pay for itself without a human signing up.

The outputs are automated rule checks, not investment advice. Verify broker-specific rules before you rely on them.

DEV Community