AI agents call schwab_option_chain 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.
This tool retrieves market data (option chain information) for a given stock symbol. It performs a read-only query without creating orders, executing trades, or modifying any account state. The tool has no side effects and poses minimal risk if misused by an AI agent, as it only exposes publicly available market data.
From the tool's definition Tool name is 'schwab_option_chain' and description states 'Get option chain for a symbol' — a retrieval operation with no modification or execution of trades.
Documented attack patterns abuse exactly the kind of access schwab_option_chain 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 schwab_option_chain:
{
"version": "1",
"default": "deny",
"tools": {
"schwab_option_chain": {}
}
}schwab_option_chain is read-only, so it stays allowed — but everything else on the server is denied unless you say otherwise.
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Get option chain for a symbol. 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 schwab_option_chain: 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.
schwab_option_chain 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 schwab_option_chain 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 schwab_option_chain. 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.
schwab_option_chain 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.