yfinance_screen_gappers
AI agents call yfinance_screen_gappers to retrieve information from Yahoo Finance MCP Server without modifying anything — typically the context-gathering step in research, monitoring, and reporting workflows, before the agent takes action elsewhere.
This tool retrieves financial market data without modifying, executing external operations, or creating financial transactions. It performs a query/filter operation to identify stocks meeting 'gapper' criteria. The empty description reduces confidence slightly, but the naming pattern and sibling context clearly indicate a Read operation with minimal blast radius.
From the tool's definition Tool name 'yfinance_screen_gappers' and sibling tools (yfinance_screen, yfinance_get_price_history, yfinance_get_ticker_info, yfinance_get_ticker_news) are all data retrieval functions. The 'screen' prefix indicates filtering/searching stock data.
Attacks that exploit this kind of access
yfinance_screen_gappers. It is categorised as a Read tool in the Yahoo Finance MCP Server MCP Server, which means it retrieves data without modifying state.
Register the Yahoo Finance MCP Server MCP server in PolicyLayer and add a rule for yfinance_screen_gappers: 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 Yahoo Finance MCP Server. Nothing to install.
yfinance_screen_gappers 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 yfinance_screen_gappers 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 yfinance_screen_gappers. 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.
yfinance_screen_gappers is provided by the Yahoo Finance MCP Server MCP server (narumiruna/yfinance-mcp). 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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