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yfinance-mcp: Instructions file for Claude Code

CLAUDE.md

yfinance-mcp CLAUDE.md is an instructions file for Claude Code from bald-newcomer/yfinance-mcp. It costs 540 tokens per session, scanned A, original, MIT.

Project instructions for a Yahoo Finance MCP server, a tool that lets an AI coding agent request stock data, news, and charts from Yahoo Finance.

In plain words
What is it for?
Use it when developing or maintaining the yfinance-mcp project, including its server and demo chatbot.
Why use it?
It explains how to install, run, test, format, and type-check the project during development.

Instructions file for Claude Code

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

This is bald-newcomer/yfinance-mcp's own configuration. It tells Claude Code how to work on yfinance-mcp 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 configures →

not rated 0repo 7mo ago A scan 540 tokens original MIT
View source ↗ bald-newcomer/yfinance-mcp
Reuse

Borrowing it

Nothing to install: this file belongs to bald-newcomer/yfinance-mcp. 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/bald-newcomer/yfinance-mcp/main/CLAUDE.md
Clone the repo
git clone --depth 1 https://github.com/bald-newcomer/yfinance-mcp

Made for: Claude Code.

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Per session 540 This file is loaded in full into every session.
When invoked 540 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 original No closer match found in the catalogue.
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 $0.00540 $0.00540
Opus 5 $0.00270 $0.00270
Sonnet 5 $0.00108 $0.00108
Haiku 4.5 $0.00054 $0.00054

Measured 8d ago against content hash f4cefacc515b, method: parsed. Prices are Anthropic first-party input rates as of 2026-09-09, from the pricing page.

Security

Grade A, and why

yfinance-mcp 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 8d 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 · 70 lines

How it starts

The opening of the file, as written. The whole thing — 70 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

Yahoo Finance MCP Server (yfmcp) - An MCP server providing tools to fetch stock data, news, and financial charts using yfinance.

Commands

# Install dependencies
uv sync

# Install with dev dependencies (for demo)
uv sync --extra dev

# Run MCP server
uv run yfmcp

# Run demo chatbot
uv run chainlit run demo.py

# Run tests
uv run pytest

# Run single test
uv run pytest tests/test_server.py::test_get_ticker_info -v

# Lint and format
uv run ruff check .
uv run ruff format .

# Type check
uv run ty src/

Architecture

MCP Server

  • src/yfmcp/server.py - Main FastMCP server with all tool implementations (get_ticker_info, get_ticker_news, search, get_top, get_price_history)
  • src/yfmcp/types.py - Literal type definitions for enums (Sector, TopType, Period, Interval, ChartType, SearchType)
  • Entry point: yfmcp.server:main via yfmcp command

Demo Chatbot

  • demo.py - Chainlit-based chatbot demo that connects to the MCP server
    • Supports both OpenAI and LiteLLM backends
    • Handles tool calling with automatic image/chart display
    • Manages persistent MCP session throughout chat lifecycle
    • Key functions:
      • get_mcp_client() - Creates MCP client connection
      • extract_tool_result() - Extracts text and images from tool results
      • convert_mcp_tools_to_openai_format() - Converts MCP tools to OpenAI format
      • handle_error() - Unified error handling and logging

Key Dependencies

MCP Server

  • mcp[cli] - FastMCP framework for MCP server
  • yfinance - Yahoo Finance data API
  • mplfinance - Financial charting library

Demo Chatbot (dev dependencies)

  • chainlit - Conversational AI framework for building chat interfaces
  • openai - OpenAI Python client (for OpenAI backend)
  • litellm - Unified LLM API wrapper (for LiteLLM backend)
  • python-dotenv - Environment variable management
  • loguru - Logging library
  • Pillow - Image processing (for WebP to PNG conversion)

Read the full file on GitHub · 70 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. 8d ago First seen · 70 lines · 540 tokens per session scan A f4cefacc515b

Subscribe to this mod's changes

yfinance-mcp CLAUDE.md is an instructions file published in the GitHub repository bald-newcomer/yfinance-mcp (0 stars, last pushed 7mo ago), licensed MIT. It adds 540 tokens to every session, about $0.0027 per session on Opus 5. A static security scan graded it A with 0 findings. No closer match exists in the catalogue, so it is treated as the original; first seen 2026-09-01.

Finance and fintech
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