update_fhir_resource

THE RISK

Medium Risk

Why update_fhir_resource needs a policy

This tool modifies existing healthcare records in AWS HealthLake, a protected health information (PHI) system. Updates are reversible (Write category), but the sensitivity is high because: (1) healthcare data is regulated (HIPAA), (2) incorrect modifications could impact patient care, (3) HealthLake stores critical medical records.

From the tool's definition Tool name 'update_fhir_resource' and description 'Update an existing FHIR resource in HealthLake' indicate modification of healthcare data.

Documented attack patterns abuse exactly the kind of access update_fhir_resource gives an agent:

POLICY

How to control update_fhir_resource

PolicyLayer is an MCP gateway — it sits between your AI agents and Prometheus MCP Server, and nothing reaches the server without passing your rules. This is the rule we recommend for update_fhir_resource:

policy.json

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

update_fhir_resource 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.

Create a free account and register Prometheus MCP Server — nothing to install.
Add this policy — paste it, or build it visually.
Point your MCP client (Claude, Cursor, anything) at your gateway URL.

LIMIT THIS TOOL →

Free to start. No card required.

EXPLORE

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Go deeper

The MCP Attack Database → Documented attack patterns against MCP deployments — and the policies that stop them.
Argument validation → Checking tool call arguments against schema and policy before they run.
Scoped token → Per-person credentials that grant a defined subset of servers and tools.
Rate Limiting MCP Tool Calls: A Practical Guide →
MCP Security: Why Prompt Guardrails Aren't Enough →

FAQ

Questions about update_fhir_resource

What does the update_fhir_resource tool do? +

Update an existing FHIR resource in HealthLake. It is categorised as a Write tool in the Prometheus 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_fhir_resource? +

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

What risk level is update_fhir_resource? +

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

Can I rate-limit update_fhir_resource? +

Yes. Add a rate_limit block to the update_fhir_resource 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_fhir_resource completely? +

Set action: deny in the PolicyLayer policy for update_fhir_resource. 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_fhir_resource? +

update_fhir_resource is provided by the Prometheus MCP Server MCP server (awslabs.prometheus-mcp-server). PolicyLayer sits as a proxy in front of this server to enforce policies before tool calls reach the server.

Enforce policy on every Prometheus MCP Server tool call.

Start from Prometheus MCP Server, add the rest of your stack, and see everything your agents can call. Then put policy on all of it.

CHECK YOUR STACK →