yahoo-finance-ai-tool

Async Yahoo Finance client + CLI (yfin) + MCP server for LLM agents. Fetches everything Yahoo Finance knows about any ticker on any world exchange: realtime quotes, OHLCV history (daily + intraday), fundamentals, key stats, technical indicators, dividends/splits/earnings calendar, news, option chains, holders, and analyst data.

Symbols use Yahoo conventions: AAPL, MSFT (US), RELIANCE.NS (NSE India), RELIANCE.BO (BSE), 7203.T (Tokyo), BMW.DE (Xetra), etc. International tickers are first-class — everything below works identically for them.

Architecture

yfin CLI (typer+rich)      MCP server "yfinance" (FastMCP: stdio + streamable-http)
        \                     /
         YahooService (facade: per-instance quoteSummary cache, concurrent snapshot)
            |— parsers.py     raw JSON -> pydantic v2 models (unwrap {"raw":..} values)
            |— indicators.py  pure-python SMA/EMA/RSI/MACD/Bollinger/ATR/Stochastic
            |— bulk.py        semaphore-bounded gather, per-symbol error isolation
            |— export.py      json / csv / parquet (pandas+pyarrow)
         YahooClient (curl_cffi AsyncSession, token-bucket rate limit,
            |                 retry+backoff, 401 -> auto crumb refresh)
         auth.py SessionStore (~/.yfinance-ai/session.json: cookies + crumb)

Why curl_cffi and not httpx

Yahoo blocks non-browser TLS fingerprints: plain curl/httpx receive HTTP 429 "Too Many Requests" on every query{1,2}.finance.yahoo.com endpoint regardless of headers (verified live 2026-06-12). curl_cffi with impersonate="chrome" presents a genuine Chrome TLS/JA3 fingerprint and gets 200s. The rest of the stack (rate limiting, retries, pooling) is our own code on top of curl_cffi.requests.AsyncSession.

Cookie + crumb auth (no credentials!)

Many endpoints (quoteSummary, quote, options) require a consent cookie plus a "crumb" CSRF token:

1. GET https://fc.yahoo.com → sets the A3 cookie (response body is a 404 — ignore it)
2. GET https://query1.finance.yahoo.com/v1/test/getcrumb → plain-text crumb
3. The crumb is appended as &crumb=... to authed endpoints.

This is bootstrapped automatically and lazily — no username/password exists in this flow. The session persists to ~/.yfinance-ai/session.json (chmod 600) and is shared by CLI, MCP, and library. On HTTP 401/403 or an "Invalid Crumb" body the client refreshes the session once and retries. If an LLM agent sees auth errors, it can self-heal by calling the yfin_login MCP tool / yfin login CLI command.

Install

cd yahoo-finance-ai-tool
uv venv && uv pip install -e ".[dev]"

CLI

Every data command accepts --json for raw model JSON. -v enables debug logs.

yfin login                      # bootstrap/refresh cookie+crumb session (optional; auto anyway)
yfin auth-status                # {"has_session": true, "has_crumb": true, ...}
yfin logout

yfin search "reliance industries"            # symbols across all exchanges + news
yfin quote AAPL MSFT RELIANCE.NS             # realtime quotes table
yfin price AAPL --range 5y --interval 1wk    # OHLCV history
yfin price AAPL --range 1d --interval 5m     # intraday
yfin fundamentals AAPL --statement income --frequency annual
yfin fundamentals RELIANCE.NS --statement balance
yfin stats AAPL                              # key stats + valuation ratios
yfin profile AAPL                            # sector/industry/summary
yfin technical AAPL --range 1y               # SMA/EMA/RSI/MACD/BB/ATR/Stoch + signals
yfin technical AAPL --series --json          # full date-aligned series
yfin events AAPL --range 10y                 # dividends, splits, earnings calendar
yfin earnings AAPL                           # EPS actual vs estimate history
yfin news AAPL --limit 10
yfin options AAPL --expiry 2026-12-18        # option chain (near-the-money shown)
yfin holders AAPL                            # institutional/fund holders
yfin analysts AAPL                           # price targets + recommendation trend
yfin snapshot AAPL                           # everything in one JSON
yfin bulk AAPL MSFT RELIANCE.NS TCS.NS --dataset price --range 5y --out prices.parquet
yfin export AAPL --what price --fmt csv --range 5y
yfin serve --transport stdio                 # MCP server (default)
yfin serve --transport http --port 8632      # MCP over streamable HTTP at /mcp

MCP server

Server name yfinance. Tools: yfin_login, yfin_auth_status, yfin_search, yfin_quote, yfin_price, yfin_fundamentals, yfin_key_stats, yfin_profile, yfin_technical, yfin_events, yfin_earnings, yfin_news, yfin_options, yfin_holders, yfin_analysts, yfin_snapshot, yfin_bulk, yfin_export.

Register with Claude Code (stdio):

claude mcp add yfinance -- uv run --directory /Users/skywalker/Development/yahoo-finance-ai-tool yfin serve

HTTP variant:

yfin serve --transport http --host 127.0.0.1 --port 8632
claude mcp add --transport http yfinance http://127.0.0.1:8632/mcp

Testing

pytest tests/unit -q                          # offline, fixture-driven (no network)
pytest tests/integration -m integration -q    # live Yahoo (needs network)
pytest tests/load -m load -q -s               # 500+ symbols x 5y, concurrency (slow)

Fixtures under tests/fixtures/ were captured live from Yahoo endpoints on 2026-06-12 (chart daily/intraday/5y-with-dividends for AAPL and RELIANCE.NS, search, quoteSummary with 21 modules, v7 multi-quote, options chain, fundamentals timeseries, and a bad-symbol error body).

Endpoints used

Limitations

• Unofficial API — Yahoo can change shapes or block at any time. The client is polite (2 req/s token bucket by default, backoff on 429) but heavy use may get an IP throttled.
• Quarterly statement line items are gone: Yahoo deprecated detailed line items in the quarterly quoteSummary statement modules (entries carry only endDate now). Annual statements still include full line items. The detailed quarterly data lives in the separate fundamentals-timeseries endpoint (fixture saved under tests/fixtures/timeseries_aapl.json; not yet wired into the service layer).
• Options are mostly available for US-listed tickers.
• Intraday intervals (1m..1h) only work for recent ranges (Yahoo limit).
• No real login/paid data — this only uses the free public endpoints.