AI agents call option_historicals to retrieve information from Open Stocks MCP without modifying anything — typically the context-gathering step in research, monitoring, and reporting workflows, before the agent takes action elsewhere.
The tool appears to fetch or query historical option pricing/performance data without modifying state. While the context is financial data, the operation itself is Read-only retrieval, not a Financial transaction. Low severity because historical data queries pose minimal risk if misused by an agent—they cannot move money or execute trades. Confidence is moderate due to the empty description.
From the tool's definition Tool name 'option_historicals' suggests retrieval of historical option data. The empty description limits certainty, but naming convention (historical + plural) and the context of a financial data server with no mutating verbs in the name indicate a query…
Documented attack patterns abuse exactly the kind of access option_historicals gives an agent:
PolicyLayer is an MCP gateway — it sits between your AI agents and Open Stocks MCP, and nothing reaches the server without passing your rules. This is the rule we recommend for option_historicals:
{
"version": "1",
"default": "deny",
"tools": {
"option_historicals": {}
}
}option_historicals is read-only, so it stays allowed — but everything else on the server is denied unless you say otherwise.
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option_historicals. It is categorised as a Read tool in the Open Stocks MCP MCP Server, which means it retrieves data without modifying state.
Register the Open Stocks MCP server in PolicyLayer and add a rule for option_historicals: 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 Stocks MCP. Nothing to install.
option_historicals 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 option_historicals 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 option_historicals. 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.
option_historicals is provided by the Open Stocks MCP server (open-agent-tools/open-stocks-mcp). PolicyLayer sits as a proxy in front of this server to enforce policies before tool calls reach the server.
Start from Open Stocks MCP, add the rest of your stack, and see everything your agents can call. Then put policy on all of it.
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152 Open Stocks MCP tools catalogued and risk-classified — across an index of 43,000+ MCP servers.