The Variance (VAR) indicator measures the dispersion of a data series from its mean, often used as a volatility indicator to identify potential trading opportunities and risk management.
AI agents call GetTimeSeriesVar 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.
GetTimeSeriesVar is a read-only analytical tool that computes and returns a statistical indicator derived from time series data. While the Twelve Data server provides financial market data (which could be used for trading decisions), this specific tool only retrieves/calculates metrics without executing trades, modifying data, or moving money.
From the tool's definition Tool retrieves and calculates a technical indicator (Variance/VAR) on financial market data. The description states it 'measures the dispersion of a data series from its mean' and is 'used as a volatility indicator to identify potential trading opportunities…
Documented attack patterns abuse exactly the kind of access GetTimeSeriesVar 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 GetTimeSeriesVar:
{
"version": "1",
"default": "deny",
"tools": {
"GetTimeSeriesVar": {}
}
}GetTimeSeriesVar is read-only, so it stays allowed — but everything else on the server is denied unless you say otherwise.
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The Variance (VAR) indicator measures the dispersion of a data series from its mean, often used as a volatility indicator to identify potential trading opportunities and risk management. 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 GetTimeSeriesVar: 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.
GetTimeSeriesVar 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 GetTimeSeriesVar 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 GetTimeSeriesVar. 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.
GetTimeSeriesVar 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.