The short answer

For a solo operator in 2026: Alpaca for the lowest-friction REST stack (200 trade req/min, $99/mo for full SIP + OPRA data), Interactive Brokers for the widest asset and venue coverage at the lowest commissions (Web API needs an IBKR Pro account), and Tradier for an options-first REST broker with no separate data fee but a 60 req/min trading cap. Verified 2026-06-07.

For a solo operator wiring a trading API in 2026, the split is clean: Alpaca for the lowest-friction REST stack (free paper, 200 trade requests/min, $99/mo for full SIP + OPRA market data), Interactive Brokers for the widest asset and venue coverage at the lowest commissions (but the Web API needs an IBKR Pro account and the brand's setup tax is real), Tradier for an options-first REST broker with no monthly fee on the data feed but a 60 requests/min trading cap. All three numbers below are from each vendor's own docs, verified 2026-06-07. The fork is rate limits and account requirements, not "which broker is good."

TL;DR

Broker Trade API rate limit Market data feed Options Account requirement Non-US
Alpaca 200 req/min1 Free IEX or $99/mo SIP + OPRA2 Yes (paid data tier) Standard brokerage account US residents + select international
Interactive Brokers ~50 msg/sec (TWS); pacing limits on data3 Per-exchange subscriptions metered Yes (deep) IBKR Pro required for Web API4 Global
Tradier 60 req/min trading, 120 req/min market data5 Included; no separate monthly fee6 Yes (core product) Tradier Brokerage account US only

Every figure verified 2026-06-07 against the vendor's official documentation. Sources at the foot of the page.

The decision is rate limits and account type, not "best broker"

All three execute equities and options. What actually shapes an AI-driven stack is two things a beginner overlooks: how many requests per minute the trading endpoint allows before it returns 429, and what kind of account or subscription grants API access at all. Get those wrong and a retry-happy agent either chews through its rate budget invisibly or can't authenticate against the live endpoint.

Alpaca: lowest friction, hard 200/min trade cap

Alpaca's Trading API is throttled at 200 requests per minute, per account; exceeding it returns HTTP 429, and Alpaca does not let users raise the cap themselves1. That 200/min applies to the trading endpoints regardless of your data tier. Market data is separate: the free Basic plan gives a real-time IEX feed (a subset of volume), a 30-symbol WebSocket cap, and the same 200 req/min; Algo Trader Plus at $99/month turns on full SIP coverage across all US exchanges, OPRA options quotes, unlimited equity WebSocket subscriptions (1,000 for options quotes), and lifts the data API to 10,000 req/min2. The trade endpoints stay at 200/min on either tier.

For a solo operator this is the simplest path: HTTPS REST, free paper trading with the same surface as live, an official MCP server, and one $99 line item if you need the real consolidated tape. The 200/min trade cap is fine for any human-paced or signal-driven strategy and only bites a high-frequency loop.

Interactive Brokers: widest coverage, the Web API needs IBKR Pro

IBKR wins on coverage (global equities, options, futures, forex, bonds, funds) and commissions (US options from $0.15-$0.65/contract tiered, or $0.65 fixed on IBKR Pro)7. Two operational facts decide whether it fits an automated stack.

First, the Web API (Client Portal API) requires an IBKR Pro account type4; the IBKR Lite tier does not get programmatic trading access. Second, the rate model is different from a clean per-minute REST quota: the legacy TWS API runs at roughly 50 messages per second to the gateway3, and historical-data requests carry explicit pacing rules (no identical request within 15 seconds, no more than ~60 historical requests in any 10-minute window)3. The Web API removes the desktop-gateway requirement of TWS but inherits IBKR's pacing discipline on market data.

The setup tax is the trade-off: more configuration, an IBKR Pro account, and pacing rules to respect, in exchange for the broadest asset and venue coverage of the three.

Tradier: options-first REST, no data subscription, tight trade cap

Tradier is the only one of the three with a fully REST, no-gateway broker API and no separate monthly market-data fee bundled into the brokerage account6. Its rate limits are split by scope and verified from the official table5:

Endpoint scope Production Sandbox
Trading (order placement) 60 req/min 60 req/min
Market data 120 req/min 60 req/min
Standard (accounts, orders read, watchlists) 120 req/min 60 req/min

Limits are enforced per minute, per access token5. The 60 req/min trading cap is the tightest of the three and the thing to design around: batch order logic, avoid polling order status in a hot loop, and lean on the market-data scope (120/min) for quotes. Commissions are $0 per stock trade and per options contract on the Tradier Pro plan ($10/month), versus $0.35 each on the free Lite tier8. The Pro subscription is a brokerage plan, not an API fee.

Which one for which operator

  • Solo operator, equities or options, wants the least wiring: Alpaca. Free paper, REST, official MCP, and a single $99/mo data upgrade when you need full SIP/OPRA. The 200/min trade cap is a non-issue below HFT.
  • Multi-asset or international, commission-sensitive at volume: Interactive Brokers. Accept the IBKR Pro requirement and the pacing rules; you get coverage and pricing nothing else here matches.
  • Options-first, US-only, allergic to data subscriptions: Tradier. No monthly data fee, $0 commissions on Pro, but design for the 60 req/min trading ceiling.

What to verify before you commit

  • Account type gating. IBKR's Web API needs IBKR Pro; Alpaca and Tradier do not gate the API behind a specific plan. Confirm your account type allows programmatic trading before building.
  • Where the rate limit lands. Alpaca's 200/min is on trading (data is 10k/min on the paid tier); Tradier splits 60/min trading vs 120/min data; IBKR uses message-rate plus historical pacing. They are not comparable as a single number.
  • Data cost is separate from the broker. Alpaca charges $99/mo for SIP+OPRA; Tradier bundles its feed; IBKR meters per-exchange subscriptions. Price the data feed, not just the commissions.
  • Paper/live parity. Alpaca and IBKR offer full-surface paper environments; Tradier ships a sandbox with lower rate limits (60/min across scopes), so load-test against production limits before going live.

Connects to

References

Footnotes

  1. Alpaca. "Is there a usage limit for the number of API calls per second?" (Trading API throttled at 200 requests/minute per account; 429 on exceed; users cannot self-raise). Verified 2026-06-07. https://alpaca.markets/support/usage-limit-api-calls ↩ ↩2

  2. Alpaca. "About Market Data API" (Basic free: IEX feed, 30-symbol WebSocket, 200 req/min; Algo Trader Plus $99/month: full SIP, OPRA options, unlimited equity WebSocket / 1,000 options-quote WebSocket, 10,000 req/min). Verified 2026-06-07. https://docs.alpaca.markets/us/docs/about-market-data-api ↩ ↩2

  3. Interactive Brokers. "TWS API: Order Limitations" and "Historical Data Limitations" (~50 messages/second; no identical historical request within 15s; ~60 historical requests per 10-minute window). Verified 2026-06-07. https://interactivebrokers.github.io/tws-api/order_limitations.html ↩ ↩2 ↩3

  4. Interactive Brokers. "Web API Documentation / Trading Web API" (live account must be IBKR Pro type to use the Web API). Verified 2026-06-07. https://www.interactivebrokers.com/campus/ibkr-api-page/web-api-trading/ ↩ ↩2

  5. Tradier. "Rate Limiting" (Production: trading 60/min, market data 120/min, standard 120/min; sandbox 60/min; per minute, per access token). Verified 2026-06-07. https://docs.tradier.com/docs/rate-limiting ↩ ↩2 ↩3

  6. Tradier. "Brokerage API FAQ" (API access included with a Tradier Brokerage account; no separate charge for API use). Verified 2026-06-07. https://documentation.tradier.com/brokerage-api/overview/faq ↩ ↩2

  7. Interactive Brokers. "Commissions: Options" (IBKR Pro US options $0.15-$0.65/contract tiered or $0.65 fixed). Verified 2026-06-07. https://www.interactivebrokers.com/en/pricing/commissions-options.php ↩

  8. Tradier. "Pricing & Plans" (Lite free with $0.35/trade and $0.35/contract; Pro $10/month with $0 stock and equity-options commissions). Verified 2026-06-07. https://tradier.com/individuals/pricing ↩

Frequently asked questions

What is the API rate limit for Alpaca vs Interactive Brokers vs Tradier in 2026?
Alpaca caps the Trading API at 200 requests/minute per account (data is 10,000/min on Algo Trader Plus). Tradier allows 60 requests/minute for trading and 120/minute for market data in production. Interactive Brokers uses a message-rate model of about 50 messages/second plus explicit historical-data pacing rules. Verified 2026-06-07.
Does the Interactive Brokers API cost anything?
The Web API itself is free, but the live account must be an IBKR Pro account type to use it; IBKR Lite does not get programmatic trading access. Commissions on IBKR Pro US options run $0.15-$0.65 per contract tiered or $0.65 fixed. Verified 2026-06-07.
How much does Alpaca charge for options market data?
Options market data requires the Algo Trader Plus plan at $99/month, which includes the OPRA options feed (1,000-symbol WebSocket cap for options quotes) plus full SIP equity coverage. The free Basic plan only provides an indicative options feed. Verified 2026-06-07.
Does Tradier charge for API access or market data?
No. API access and the market-data feed are included with a Tradier Brokerage account at no separate monthly fee. Commissions are $0 on stocks and equity options with the Tradier Pro plan ($10/month), or $0.35 each on the free Lite tier. Verified 2026-06-07.
Which broker API is best for a solo AI trader?
Alpaca for most solo operators: free paper trading, REST, an official MCP server, and a single $99/month upgrade for full SIP and OPRA data. Choose Interactive Brokers if you need multi-asset or international coverage, or Tradier if you are options-first and want no data subscription.