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yfinance-mcp-server MCP server · F · ToolBench

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yfinance-mcp-server

github.com/SzeMeng76/yfinance-mcp-server

unofficial Yahoo Finance API MCP Server - A Model Context Protocol server implementation for Yahoo Finance API

2026-07-28+STDIO5 tools

46/100

Definition Quality62

Protocol Readiness50

Supportability18

Spec posture

Inferred effective spec 2026-07-28+·current baseline 2026-07-28

Static source inference · medium confidence

Current-spec patterns detected

Summary

Server defines 5 tools with Zod schemas and basic descriptions. All tools are READ_ONLY financial data queries. Naming follows verb_noun pattern (yahoo_*). Schemas are present and typed. However, descriptions are generic (avg ~80 chars, below 194-char baseline), lack WHEN/WHY guidance, and omit output schema documentation. Parameters lack detailed constraints (e.g., no min/max for quotesCount, no format hints for dates). Error handling returns raw error messages without recovery guidance. No tool annotations (readOnlyHint, etc.). Output is always JSON text blob, no structured response schema documented.

Tools (5)

yahoo_chartread onlysource verified63/100

Retrieves chart data for a stock symbol with customizable time period and interval

yahoo_quoteread onlysource verified62/100

Retrieves real-time quote information for one or more stock symbols

yahoo_quote_summaryread onlysource verified62/100

Retrieves detailed summary information for a stock symbol including price and summary details

yahoo_searchread onlysource verified58/100

Searches for stocks and related information on Yahoo Finance

yahoo_stock_historyread onlysource verified63/100

Retrieves historical stock data for a given symbol with customizable period, interval, and optional parameters

Issues (5)

HIGHtool-description ↗

Descriptions lack actionable context. All 5 tools have generic 40 - 80 char descriptions that state WHAT but omit WHEN to use, dependencies, or prerequisites. E.g., 'Retrieves historical stock data' does not explain when to call this vs yahoo_chart, or that period/period1 are mutually exclusive.

yahoo_stock_historyyahoo_chartyahoo_quoteyahoo_searchyahoo_quote_summary

HIGHresponse-shaper ↗

Output schema not documented. All tools return JSON text in a content array, but the structure of that JSON (fields, types, nesting) is never specified. LLMs cannot plan downstream calls or extract fields reliably.

yahoo_stock_historyyahoo_chartyahoo_quoteyahoo_searchyahoo_quote_summary

HIGHconstrained-input ↗

Parameter constraints missing. quotesCount, newsCount, and other numeric params lack min/max bounds. Date params (period1, period2) lack format hints (ISO 8601 vs epoch vs string). LLMs will pass invalid values.

Recommendations

Expand each tool description to 100 - 200 chars. Include: what it returns, when to use it vs similar tools, and any prerequisites. E.g., 'Fetch historical OHLCV data for a stock. Use this for backtesting or trend analysis. Requires a valid stock symbol; call yahoo_search() first if unsure.'
Document output schema for each tool. Specify the JSON structure returned: field names, types, and nesting. E.g., 'Returns array of {date, open, high, low, close, volume, adjClose}.'
Add min/max constraints to numeric params. E.g., quotesCount: 1 - 100 (default 10), newsCount: 1 - 50 (default 5). Add format hints to date params: 'ISO 8601 string (YYYY-MM-DD) or Date object.'
Enhance error messages with recovery hints. E.g., 'Symbol "XYZ" not found. Try yahoo_search("XYZ") to find the correct ticker.' Categorize errors: retryable (network timeout), user-fixable (invalid symbol), or fatal (API key expired).
Add tool annotations. Mark all 5 tools with readOnlyHint: true in the tool definition. This signals to LLMs that these tools are safe to call without confirmation and can be retried.

Score history

Overall score trend

First recorded score · v2 rubric

46/100

Scored	Grade	Overall	Spec posture	Rubric
2026-09-23	F	46	2026-07-28+	v2