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yfinance-mcp-server: Instructions file for Claude Code

CLAUDE.md

yfinance-mcp-server CLAUDE.md is an instructions file for Claude Code from mokemokechicken/yfinance-mcp-server. It costs 1,303 tokens per session, scanned A, original, from a forked repository, ISC.

Project instructions for an unofficial Yahoo Finance API MCP server. Yahoo Finance provides financial market data, and an API lets software request that data; MCP is a way for AI tools to use such services.

In plain words
What is it for?
Use it when building, developing, checking, formatting, linting, type-checking, or testing this TypeScript server.
Why use it?
It gives Claude Code the repository overview, development commands, testing steps, and architecture needed to work on the project.

Instructions file for Claude Code

Written for Claude Code: the file is CLAUDE.md. Also seen: mentions CLAUDE.md; mentions Claude Code.

This is mokemokechicken/yfinance-mcp-server's own configuration. It tells Claude Code how to work on yfinance-mcp-server itself, so it is not a mod to install elsewhere. Copy it as a starting point and replace the rules that are about this project. Everything yfinance-mcp-server configures →

not rated 1repo 5mo ago A scan 1,303 tokens fork ISC
View source ↗ mokemokechicken/yfinance-mcp-server
Reuse

Borrowing it

Nothing to install: this file belongs to mokemokechicken/yfinance-mcp-server. Take a copy, put it at the same path in your own repository, and replace the rules that are about this project with yours.

Copy the file
curl -O https://raw.githubusercontent.com/mokemokechicken/yfinance-mcp-server/main/CLAUDE.md
Clone the repo
git clone --depth 1 https://github.com/mokemokechicken/yfinance-mcp-server

Made for: Claude Code.

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Per session 1,303 This file is loaded in full into every session.
When invoked 1,303 The same file — it is already loaded in full.
Security scan A 0 findings. A grade says what 26 rules found in the file — not that it is safe.
Origin fork From a forked repository.
Token cost

What it costs to keep this loaded

Counted locally with the o200k_base tokenizer, which is exact for GPT models; Claude uses its own tokenizer and its counts differ. Treat this as one consistent yardstick across the catalogue rather than a bill. Prices are per million input tokens.

ModelPer sessionOnce invoked
Fable 5.1 $0.01303 $0.01303
Opus 5 $0.00651 $0.00651
Sonnet 5 $0.00261 $0.00261
Haiku 4.5 $0.00130 $0.00130

Measured 9d ago against content hash e0878094260a, method: parsed. Prices are Anthropic first-party input rates as of 2026-09-10, from the pricing page.

Security

Grade A, and why

yfinance-mcp-server CLAUDE.md scanned grade A with 0 findings against 26 rules in 11 categories — prompt injection, anti-refusal, data exfiltration, privilege escalation, supply chain, agent snooping, system-prompt leakage, SSRF and excessive agency — measured 9d ago.

A static scan of the body, not an audit. Every finding is printed with the line that produced it so you can judge whether it matters here. A mod is markdown that instructs an agent; that is exactly why what it instructs is worth reading.

Nothing flagged

None of the 26 patterns this scan looks for appear in this file: no shell pipes, no recursive deletes, no credential paths, no hidden text, no instruction-override or anti-refusal phrasing, no agent-config snooping. That is not a guarantee, it is the absence of the things that are checkable.

CLAUDE.md · 90 lines

How it starts

The opening of the file, as written. The whole thing — 90 lines — stays where its author put it; the contents beside it link to each section on GitHub.

CLAUDE.md

This file provides guidance to Claude Code (claude.ai/code) when working with code in this repository.

Project Overview

This is an unofficial Yahoo Finance API MCP (Model Context Protocol) server that provides AI-friendly comprehensive stock market analysis through Yahoo Finance. The server is built with TypeScript and uses the @modelcontextprotocol/sdk framework with a comprehensive technical indicators library.

Common Development Commands

  • npm run build - Build the project using esbuild (creates bundled output in build/index.js)
  • npm run dev - Start development server with file watching using tsx
  • npm run lint - Run Biome linter on src/ folder
  • npm run lint:fix - Run Biome linter with automatic fixes
  • npm run format - Format code using Biome
  • npm run check - Run Biome lint and format checks
  • npm run check:fix - Run Biome lint and format with automatic fixes
  • npm run typecheck - Run TypeScript type checking
  • npm test - Run all tests in tests/ directory using tsx test runner
  • npm run test:individual - Run individual test files with tsx --test
  • npm install - Install dependencies

Make Commands

  • make build - Build the project
  • make test - Run tests
  • make lint - Run linter
  • make check - Run format/lint checks
  • make typecheck - Run TypeScript type checking
  • make check-all - Run all checks (build, test, lint, check, typecheck)
  • make prepare - Run all checks and prepare for publishing (npm pack --dry-run)
  • make publish - Build, test, lint, and publish to npm

Project Architecture

  • Entry Point: src/index.ts contains the MCP server implementation with the main getStockAnalysis tool
  • CLI Entry Point: src/cli.ts provides a local command-line wrapper that reuses the same analysis pipeline
  • Technical Indicators Library: src/lib/technical-indicators/ contains a comprehensive technical analysis system:
    • Core Components: TechnicalAnalyzer class for coordinated analysis with AI-friendly reporting
    • Individual Indicators: RSI (extended), MACD, Moving Averages, Bollinger Bands, Stochastic, VWAP, Volume Analysis, Cross Detection
    • Financial Indicators: Enterprise financial metrics, moving average deviation analysis
    • Utilities: Calculator, DataProcessor, ValidationUtils, Japanese report generator
    • Type System: Comprehensive TypeScript interfaces and error classes with Graceful Degradation
  • MCP Server: Uses @modelcontextprotocol/sdk to create a server that communicates via stdio
  • Yahoo Finance Integration: Uses yahoo-finance2 library to fetch stock data and financial metrics
  • Testing: Comprehensive test suite covering individual indicators and utility functions

Read the full file on GitHub · 90 lines

Changes

What this file has done since we first saw it

Hashed on every crawl. A supply-chain change to an agent config is a question of when, not whether, so the history is kept rather than the latest state alone.

  1. 9d ago First seen · 90 lines · 1,303 tokens per session scan A e0878094260a

Subscribe to this mod's changes

yfinance-mcp-server CLAUDE.md is an instructions file published in the GitHub repository mokemokechicken/yfinance-mcp-server (1 stars, last pushed 5mo ago), licensed ISC. It adds 1,303 tokens to every session, about $0.0065 per session on Opus 5. A static security scan graded it A with 0 findings. It comes from a forked repository.

Finance and fintech
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