The Percent B (%B) is a component of the Bollinger Bands indicator, measuring the position of a security
AI agents call GetTimeSeriesPercent_B 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 is a data retrieval tool that returns a calculated technical indicator based on historical price data. It has no side effects, does not modify any data, does not execute code or external operations, and does not involve financial transactions. It is purely informational analysis of market data, consistent with the 'Read' category for retrieval and query operations.
From the tool's definition Tool retrieves the Percent B (%B) indicator value by querying historical time series data. The description states it 'measures the position of a security' within Bollinger Bands, which is a technical analysis calculation performed on existing market data.
Documented attack patterns abuse exactly the kind of access GetTimeSeriesPercent_B 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 GetTimeSeriesPercent_B:
{
"version": "1",
"default": "deny",
"tools": {
"GetTimeSeriesPercent_B": {}
}
}GetTimeSeriesPercent_B is read-only, so it stays allowed — but everything else on the server is denied unless you say otherwise.
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The Percent B (%B) is a component of the Bollinger Bands indicator, measuring the position 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 GetTimeSeriesPercent_B: 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.
GetTimeSeriesPercent_B 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 GetTimeSeriesPercent_B 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 GetTimeSeriesPercent_B. 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.
GetTimeSeriesPercent_B 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.