AI agents call getDistance to retrieve information from FitBit MCP without modifying anything — typically the context-gathering step in research, monitoring, and reporting workflows, before the agent takes action elsewhere.
The tool appears to fetch distance data from Fitbit's health and fitness metrics. No side effects, modifications, or destructive operations are indicated. The 'get' prefix and alignment with other data retrieval tools on this server confirm a Read classification. Confidence is slightly reduced due to the empty description, but the pattern is clear.
From the tool's definition Tool name 'getDistance' with prefix 'get' indicates data retrieval. Sibling tools (getActiveZoneMinutes, getActivities, getBadges, getBodyMeasurements, getCalories, getDevices, getFloorsClimbed, getFoodLogs, getHeartRate, getLifetimeStats) are all Read…
Documented attack patterns abuse exactly the kind of access getDistance gives an agent:
PolicyLayer is an MCP gateway — it sits between your AI agents and FitBit MCP, and nothing reaches the server without passing your rules. This is the rule we recommend for getDistance:
{
"version": "1",
"default": "deny",
"tools": {
"getDistance": {}
}
}getDistance is read-only, so it stays allowed — but everything else on the server is denied unless you say otherwise.
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getDistance. It is categorised as a Read tool in the FitBit MCP MCP Server, which means it retrieves data without modifying state.
Register the FitBit MCP server in PolicyLayer and add a rule for getDistance: 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 FitBit MCP. Nothing to install.
getDistance 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 getDistance 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 getDistance. 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.
getDistance is provided by the FitBit MCP server (nitayrabi/fitbit-mcp). PolicyLayer sits as a proxy in front of this server to enforce policies before tool calls reach the server.
Start from FitBit MCP, add the rest of your stack, and see everything your agents can call. Then put policy on all of it.
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16 FitBit MCP tools catalogued and risk-classified — across an index of 43,000+ MCP servers.