The Maximum Index (MAXINDEX) returns the index of the highest value in a data series over a specified period, providing information about the timing of extreme price movements.
AI agents call GetTimeSeriesMaxIndex 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 queries financial time series data to compute a statistic (maximum value index) and return the result. It has no side effects, does not execute code or commands, does not create or modify data, does not delete anything, and does not involve financial transactions. It is purely a data retrieval and analytical operation, consistent with the Read category for analytics tools on financial data APIs.
From the tool's definition Tool returns 'the index of the highest value in a data series over a specified period' — it retrieves and analyzes historical data without modifying, deleting, or executing any operations.
Documented attack patterns abuse exactly the kind of access GetTimeSeriesMaxIndex 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 GetTimeSeriesMaxIndex:
{
"version": "1",
"default": "deny",
"tools": {
"GetTimeSeriesMaxIndex": {}
}
}GetTimeSeriesMaxIndex is read-only, so it stays allowed — but everything else on the server is denied unless you say otherwise.
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The Maximum Index (MAXINDEX) returns the index of the highest value in a data series over a specified period, providing information about the timing of extreme price movements. 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 GetTimeSeriesMaxIndex: 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.
GetTimeSeriesMaxIndex 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 GetTimeSeriesMaxIndex 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 GetTimeSeriesMaxIndex. 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.
GetTimeSeriesMaxIndex 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.