The Midprice (MIDPRICE) indicator calculates the average of a security
AI agents call GetTimeSeriesMidPrice to retrieve information from Twelve Data 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 and computes financial market data (midprice of a security) with no side effects, data modification, code execution, or financial transactions. It falls squarely within the Read category. Severity is low because unauthorized access to historical price data presents minimal risk compared to tools that execute trades or delete data.
From the tool's definition Tool name 'GetTimeSeriesMidPrice' uses 'Get' prefix and description states it 'calculates the average of a security', indicating data retrieval and computation without modification.
Documented attack patterns abuse exactly the kind of access GetTimeSeriesMidPrice gives an agent:
PolicyLayer is an MCP gateway — it sits between your AI agents and Twelve Data MCP Server, and nothing reaches the server without passing your rules. This is the rule we recommend for GetTimeSeriesMidPrice:
{
"version": "1",
"default": "deny",
"tools": {
"GetTimeSeriesMidPrice": {}
}
}GetTimeSeriesMidPrice is read-only, so it stays allowed — but everything else on the server is denied unless you say otherwise.
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The Midprice (MIDPRICE) indicator calculates the average of a security. It is categorised as a Read tool in the Twelve Data MCP Server MCP Server, which means it retrieves data without modifying state.
Register the Twelve Data MCP Server MCP server in PolicyLayer and add a rule for GetTimeSeriesMidPrice: 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 Twelve Data MCP Server. Nothing to install.
GetTimeSeriesMidPrice 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 GetTimeSeriesMidPrice 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 GetTimeSeriesMidPrice. 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.
GetTimeSeriesMidPrice is provided by the Twelve Data MCP Server MCP server (twelvedata/mcp). PolicyLayer sits as a proxy in front of this server to enforce policies before tool calls reach the server.
Deterministic rules across all 186 Twelve Data MCP Server tools. Per-identity grants. Full audit log. Live in minutes. Nothing to install.
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186 Twelve Data MCP Server tools catalogued and risk-classified — across an index of 42,500+ MCP servers.