Best Stock Market APIs for AI Builders (Oct 2026)
By Jay Rocco, Chief Editor, FullStack Alpha. Updated . Prices checked on each vendor's own site.
We ranked 71 stock market APIs for AI builders in our directory and kept the top 15. Each one has a verified price, a plain "best for" and "watch out" note, and links to deeper reviews where FullStack Alpha has tested it.
Of the 15 stock market APIs for AI builders ranked here, 15 of 15 have a free plan, the cheapest paid plan starts at $7.99/mo, 15 offer an API.
Editor's pick: QuantConnect, tested hands-on (how we test).
The 15 best, in order
1. QuantConnect
Institutional-grade cloud quant platform allowing users to design AI strategies via natural language.
Best for: Coders testing systematic strategies; Multi-asset backtests with live deploy; Quant teams needing shared research
Watch out: Paid tiers start at $84/mo and team tiers need at least 2 seats.
Price: Free, paid from $84/mo. Features: AI chat assistant, Alerts, API access, Automated trading, Backtesting, Broker connection, Fundamentals, Global markets, MCP / AI connector, Paper trading, Strategy builder.
2. Composer
Visual platform for building algorithmic trading strategies using plain-English logic blocks.
Best for: No-code strategy automation; Backtesting before investing; Rules-based portfolio rebalancing
Watch out: Free tier automates only one strategy, so running several needs a paid plan.
Price: Free, paid from $10/mo. Features: AI chat assistant, API access, Automated trading, Backtesting, Broker connection, MCP / AI connector, Managed portfolios, Strategy builder.
3. Quartr
Earnings calls, live transcripts, filings and slides with AI chat and an MCP link to Claude.
Best for: Listening to live earnings calls; Searching call transcripts and slides; Analysts tracking many companies
Watch out: Pro pricing is quote only, so the desktop product cost is unknown.
Price: Free plan. Features: AI chat assistant, Alerts, API access, Earnings calls, Fundamentals, MCP / AI connector, Mobile app.
4. Portfolio123
Quant workbench for ranking systems, point-in-time backtests and machine-learning stock predictors.
Best for: Factor based stock screening; Backtesting rule based strategies; Quant investors who like data
Watch out: Backtest length and features grow with the plan, and AI Factor training carries extra usage fees.
Price: Free, paid from $25/mo. Features: API access, Backtesting, Broker connection, Charting, Fundamentals, Global markets, Stock screener, Community, Strategy builder.
5. Alpaca
API-first brokerage enabling developers to deploy algorithmic and AI trading systems natively.
Best for: Developers building trading bots; Commission-free API trading; Testing with paper trading
Watch out: The free data feed is IEX only and delayed, so real-time full-market data costs $99 a month.
Price: Free, paid from $99/mo. Features: API access, Automated trading, Backtesting, Broker connection, Crypto, MCP / AI connector, Options analytics, Paper trading.
6. Bigdata.com
An AI research engine that ingests filings, transcripts, and reports to return synthesized, source-linked answers.
Best for: Grounding AI agents in finance data; Developers building research agents; Claude or ChatGPT connector users
Watch out: Usage is billed by credits, and a single query can cost $0.57 to $1.82.
Price: Free, paid from $40/mo. Features: AI chat assistant, API access, Earnings calls, Fundamentals, MCP / AI connector, News and sentiment.
7. TradesViz
Trading journal with a free forever tier, AI analytics and a built-in simulator
Best for: Free trade journaling; Options and stats nerds; Linking an AI assistant via MCP
Watch out: Premium analytics and the AI coach sit behind paid Pro or Platinum tiers.
Price: Free, paid from $14.99/mo. Features: AI chat assistant, API access, Backtesting, Broker connection, Charting, MCP / AI connector, Options analytics, Portfolio tracking.
8. GuruFocus
Value investing research site with 30 years of financials, guru portfolio tracking, GuruAI chat and an MCP server.
Best for: Guru portfolio tracking; Value investing screens; Insider and politician trades
Watch out: Plan prices did not load on the pricing page.
Price: Free plan. Features: API access, Earnings calls, Fundamentals, Insider and Congress trades, MCP / AI connector, Stock screener, Community.
9. EODHD
Financial data API with 30 years of prices and fundamentals, plus an official MCP server for Claude and ChatGPT.
Best for: Developers building stock apps; Global market price history; Quick API prototypes
Watch out: The free plan allows only 20 API calls a day and 1 year of history.
Price: Free, paid from $19.99/mo. Features: API access, Fundamentals, Insider and Congress trades, Global markets, MCP / AI connector.
10. WunderTrading
A trading automation platform with copy trading and bots that connects signals to brokerage execution.
Best for: Automating TradingView alerts; Crypto DCA and grid bots; Trying bots on a free plan
Watch out: Free plan limits bots to one of each type.
Price: Free plan. Features: Alerts, API access, Automated trading, Backtesting, Broker connection, Crypto, MCP / AI connector, Paper trading, Stock screener.
11. BacktestLoop
AI backtesting platform that turns a plain-English strategy into editable Python and tests it on market history.
Best for: Testing ideas in plain English; Python-curious strategy builders; Cheap backtesting for side traders
Watch out: Free plan is a one-time 15 credits, and paper trading needs a paid plan.
Price: Free, paid from $7.99/mo. Features: AI chat assistant, API access, Backtesting, Charting, Crypto, MCP / AI connector, Paper trading, Strategy builder.
12. FlashAlpha
Options analytics API and free dashboards for gamma exposure, dealer positioning and vol surfaces.
Best for: Gamma exposure research; Quants backtesting options data; Feeding options data to AI
Watch out: Free tier allows just 5 requests a day with delayed data.
Price: Free, paid from $79/mo. Features: API access, Backtesting, MCP / AI connector, Options analytics, Stock screener.
13. MotiveWave
Desktop trading platform with study and harmonic pattern scanners for swing setups
Best for: Elliott Wave and order flow traders; Futures and forex chartists; Traders who prefer buying software
Watch out: The free Community edition allows only one broker or data feed per workspace and skips live trading.
Price: Free, paid from $22.50/mo. Features: API access, Backtesting, Broker connection, Charting, Crypto, Mobile app, Stock screener, Strategy builder, AI trade signals.
14. TradeStation
Active-trader broker with an official MCP that links your account to Claude or ChatGPT for research and order previews.
Best for: Active traders; Futures and options; Algo developers using API
Watch out: International clients pay a $5 ticket charge per trade.
Price: Free plan. Features: API access, Charting, MCP / AI connector, Mobile app, Paper trading, Stock screener.
15. Marx Finance
Free platform where AI agents debate market news and post bullish or bearish signals on US tickers.
Best for: Watching AI agents debate markets; Developers registering trading agents; Free sentiment signals
Watch out: Signals come from autonomous AI agents, so they are experimental and carry no track record guarantee.
Price: Free plan. Features: AI chat assistant, API access, MCP / AI connector, News and sentiment, Price forecasts, Community, AI trade signals.
Ranked by Directory Rank (public ratings, review volume, buzz, free access and AI depth) plus fit for this job. How we rank.
Questions people ask
What is the best stock market API for AI builder right now?
QuantConnect holds the top Directory Rank on this list as of Oct 2026. It fits best for coders testing systematic strategies. The right pick still depends on your trading style and budget, so check the "best for" notes on each entry.
Is there a free option?
Yes. 15 of the 15 tools here have a free plan. QuantConnect is the highest-ranked one, but note: paid tiers start at $84/mo and team tiers need at least 2 seats.
What is the cheapest paid plan on this list?
BacktestLoop starts at $7.99 per month (monthly equivalent, checked Oct 2026). Prices change often, so confirm on the vendor's pricing page before you pay.
Which of these connect to ChatGPT, Claude or your own code?
15 tools on this list offer an API and 13 offer an MCP server or official AI connector. QuantConnect, Composer, Quartr lead on MCP support.
How is this list ranked?
Every tool gets a Directory Rank built from public review ratings (adjusted for how many reviews exist), review volume, current buzz, free access and how deep its AI features go. No tool can pay for a higher position. The full formula is on our How We Rank page.