yahoo_chart
AI agents call yahoo_chart to retrieve information from YFinance MCP Server without modifying anything — typically the context-gathering step in research, monitoring, and reporting workflows, before the agent takes action elsewhere.
The tool appears to retrieve chart data from Yahoo Finance based on context (server purpose and sibling tools like yahoo_quote, yahoo_quote_summary, yahoo_stock_history). Chart retrieval is a read-only operation with no side effects. Empty description prevents higher confidence, but the context strongly indicates read-only functionality consistent with the server's stated purpose of providing access to market data.
From the tool's definition Tool name 'yahoo_chart' and server description indicating 'retrieval of real-time quotes, historical data, charts' suggest data retrieval without modification. Empty tool description reduces confidence slightly.
Attacks that exploit this kind of access
yahoo_chart. It is categorised as a Read tool in the YFinance MCP Server MCP Server, which means it retrieves data without modifying state.
Register the YFinance MCP Server MCP server in PolicyLayer and add a rule for yahoo_chart: allow, deny, rate-limit, or require approval. Point your MCP client at the PolicyLayer proxy URL and the rule is enforced on every call, before it reaches YFinance MCP Server. Nothing to install.
yahoo_chart is a Read tool with low risk. Read-only tools are generally safe to allow by default.
Yes. Add a rate_limit block to the yahoo_chart rule in your PolicyLayer policy. For example, setting max: 10 and window: 60 limits the tool to 10 calls per minute. Rate limits are tracked per agent session and reset automatically.
Set action: deny in the PolicyLayer policy for yahoo_chart. The AI agent will receive a policy violation error and cannot call the tool. You can also include a reason field to explain why the tool is blocked.
yahoo_chart is provided by the YFinance MCP Server MCP server (szemeng76/yfinance-mcp-server). PolicyLayer sits as a proxy in front of this server to enforce policies before tool calls reach the server.
Every MCP server has a record like this.
Type a name, get the same breakdown: verified identity, auth posture, risk grade, capabilities, recommended policy.
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