Query health metrics ingested from iPhone/wearable. Returns recent values, daily/weekly averages, or trend summary (first half vs second half of period).
AI agents call health_metrics to retrieve information from Personal Brain without modifying anything — typically the context-gathering step in research, monitoring, and reporting workflows, before the agent takes action elsewhere.
This tool performs semantic and quantitative queries on existing health data from wearables. It retrieves, aggregates, and summarizes information without creating, modifying, deleting, or executing external operations. The blast radius of misuse is minimal—an AI agent could only exfiltrate personal health data, not alter it or cause financial/operational harm. Classification as Read is appropriate.
From the tool's definition Tool description explicitly states 'Query health metrics' and 'Returns recent values, daily/weekly averages, or trend summary' — all retrieval operations with no modification or deletion capability.
Attacks that exploit this kind of access
Query health metrics ingested from iPhone/wearable. Returns recent values, daily/weekly averages, or trend summary (first half vs second half of period). It is categorised as a Read tool in the Personal Brain MCP Server, which means it retrieves data without modifying state.
Register the Personal Brain MCP server in PolicyLayer and add a rule for health_metrics: 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 Personal Brain. Nothing to install.
health_metrics 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 health_metrics 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 health_metrics. 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.
health_metrics is provided by the Personal Brain MCP server (phantomts/personal-brain-mcp). PolicyLayer sits as a proxy in front of this server to enforce policies before tool calls reach the server.
Every MCP server has a record like this.
Type a name, get the same breakdown: verified identity, auth posture, risk grade, capabilities, recommended policy.
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