AI agents call stock_price to retrieve information from Open Paper Trading MCP without modifying anything — typically the context-gathering step in research, monitoring, and reporting workflows, before the agent takes action elsewhere.
This tool retrieves or queries publicly available stock market data (current price and basic metrics) without modifying, executing, or affecting any account or market state. It is a read-only operation with minimal security risk, even in the context of a paper trading platform. The blast radius of misuse is negligible—an AI agent cannot cause harm by querying stock prices.
From the tool's definition Tool name 'stock_price' and description 'Get current stock price and basic metrics' indicate retrieval of market data with no side effects.
Documented attack patterns abuse exactly the kind of access stock_price gives an agent:
PolicyLayer is an MCP gateway — it sits between your AI agents and Open Paper Trading MCP, and nothing reaches the server without passing your rules. This is the rule we recommend for stock_price:
{
"version": "1",
"default": "deny",
"tools": {
"stock_price": {}
}
}stock_price is read-only, so it stays allowed — but everything else on the server is denied unless you say otherwise.
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Get current stock price and basic metrics. It is categorised as a Read tool in the Open Paper Trading MCP MCP Server, which means it retrieves data without modifying state.
Register the Open Paper Trading MCP server in PolicyLayer and add a rule for stock_price: 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 Open Paper Trading MCP. Nothing to install.
stock_price 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 stock_price 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 stock_price. 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.
stock_price is provided by the Open Paper Trading MCP server (open-agent-tools/open-paper-trading-mcp). PolicyLayer sits as a proxy in front of this server to enforce policies before tool calls reach the server.
Start from Open Paper Trading MCP, add the rest of your stack, and see everything your agents can call. Then put policy on all of it.
Free to start. No card required.
44 Open Paper Trading MCP tools catalogued and risk-classified — across an index of 43,000+ MCP servers.