The High, Low, Close Average (HLC3) indicator calculates the average of a security
AI agents call GetTimeSeriesHlc3 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 pre-calculated or derived financial market data (HLC3 indicator values). It performs no modifications, deletions, financial transactions, or code execution. It is purely a read operation querying historical or current market data from the Twelve Data API. The low severity reflects that misuse would only result in unauthorized data access, not financial loss or system compromise.
From the tool's definition Tool name 'GetTimeSeriesHlc3' and description indicate retrieval of a calculated financial indicator (average of high, low, close prices).
Documented attack patterns abuse exactly the kind of access GetTimeSeriesHlc3 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 GetTimeSeriesHlc3:
{
"version": "1",
"default": "deny",
"tools": {
"GetTimeSeriesHlc3": {}
}
}GetTimeSeriesHlc3 is read-only, so it stays allowed — but everything else on the server is denied unless you say otherwise.
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The High, Low, Close Average (HLC3) 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 GetTimeSeriesHlc3: 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.
GetTimeSeriesHlc3 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 GetTimeSeriesHlc3 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 GetTimeSeriesHlc3. 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.
GetTimeSeriesHlc3 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.