update_health_data · Garmin MCP Server MCP: Risk & Policy

WHAT IT DOES

What update_health_data does on Garmin MCP Server

AI agents use update_health_data to create or update resources in Garmin MCP Server — usually the action step of a workflow, after the agent has gathered context. Every call changes real data in your Garmin MCP Server environment.

WHY IT NEEDS A POLICY

Why update_health_data needs a policy

This tool modifies user health metrics (weight, hydration) in a persistent backend system. While the changes are reversible (data can be corrected later) and do not delete or destroy data, they constitute writes that alter the user's health record state.

From the tool's definition Tool name 'update_health_data' and description explicitly state it 'Update[s] weight or hydration data' — a reversible modification operation that creates or alters personal health records in Garmin Connect.

Attacks that exploit this kind of access

Recommended rule Ready

Verdict

update_health_data Rate-limited

update_health_data stays usable, but capped — an agent stuck in a loop can't make hundreds of changes a minute. Everything else on the server is denied unless you say otherwise.

View as policy code

policy.json

{
  "version": "1",
  "default": "deny",
  "tools": {
    "update_health_data": {
      "limits": [
        {
          "counter": "update_health_data_rate",
          "window": "minute",
          "max": 30,
          "scope": "grant"
        }
      ]
    }
  }
}

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Instant setup, no code required.

PolicyLayer is an MCP gateway: every tool call is checked against your rule before it reaches Garmin MCP Server, so you can run agents against it safely.

FAQ

Questions about update_health_data

What does the update_health_data tool do? +

Update weight or hydration data in Garmin Connect. It is categorised as a Write tool in the Garmin MCP Server MCP Server, which means it can create or modify data. Consider rate limits to prevent runaway writes.

How do I enforce a policy on update_health_data? +

Register the Garmin MCP Server MCP server in PolicyLayer and add a rule for update_health_data: 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 Garmin MCP Server. Nothing to install.

What risk level is update_health_data? +

update_health_data is a Write tool with medium risk. Write tools should be rate-limited to prevent accidental bulk modifications.

Can I rate-limit update_health_data? +

Yes. Add a rate_limit block to the update_health_data 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.

How do I block update_health_data completely? +

Set action: deny in the PolicyLayer policy for update_health_data. 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.

What MCP server provides update_health_data? +

update_health_data is provided by the Garmin MCP Server MCP server (j4sun/garmin-mcp). PolicyLayer sits as a proxy in front of this server to enforce policies before tool calls reach the server.