AI agents call get_market_hours to retrieve information from Paper 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 static reference data (market hours) without modifying, executing transactions, or affecting any accounts or positions. It is purely informational and read-only, with minimal risk even if misused by an AI agent.
From the tool's definition Tool name 'get_market_hours' and description 'Get market hours for an exchange' indicate a query operation that retrieves informational data about market operating times with no side effects.
Documented attack patterns abuse exactly the kind of access get_market_hours gives an agent:
PolicyLayer is an MCP gateway — it sits between your AI agents and Paper MCP Server, and nothing reaches the server without passing your rules. This is the rule we recommend for get_market_hours:
{
"version": "1",
"default": "deny",
"tools": {
"get_market_hours": {}
}
}get_market_hours is read-only, so it stays allowed — but everything else on the server is denied unless you say otherwise.
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Get market hours for an exchange. It is categorised as a Read tool in the Paper MCP Server MCP Server, which means it retrieves data without modifying state.
Register the Paper MCP Server MCP server in PolicyLayer and add a rule for get_market_hours: 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 Paper MCP Server. Nothing to install.
get_market_hours 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 get_market_hours 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 get_market_hours. 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.
get_market_hours is provided by the Paper MCP Server MCP server (paperinvest/mcp-server). PolicyLayer sits as a proxy in front of this server to enforce policies before tool calls reach the server.
Start from Paper MCP Server, add the rest of your stack, and see everything your agents can call. Then put policy on all of it.
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23 Paper MCP Server tools catalogued and risk-classified — across an index of 43,000+ MCP servers.