write_fhir_resource · MCP FHIR Server MCP: Risk & Policy

WHAT IT DOES

What write_fhir_resource does on MCP FHIR Server

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

WHY IT NEEDS A POLICY

Why write_fhir_resource needs a policy

The tool modifies healthcare records (FHIR resources) which are sensitive personal medical data. While reversible (Write rather than Destructive), misuse could alter patient records, treatment plans, or clinical data with serious consequences. Severity is high because healthcare data integrity is critical; confidence is slightly reduced due to empty tool description, but the name and server context are clear.

From the tool's definition Tool name 'write_fhir_resource' and server description stating 'write access to any FHIR-compliant healthcare API' and 'resource management' indicate create/modify operations on healthcare data.

Attacks that exploit this kind of access

Recommended rule Ready

Verdict

write_fhir_resource Rate-limited

write_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.

View as policy code

policy.json

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

LIMIT THIS TOOL →

Instant setup, no code required.

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

FAQ

Questions about write_fhir_resource

What does the write_fhir_resource tool do? +

write_fhir_resource. It is categorised as a Write tool in the MCP FHIR 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 write_fhir_resource? +

Register the MCP FHIR Server MCP server in PolicyLayer and add a rule for write_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 MCP FHIR Server. Nothing to install.

What risk level is write_fhir_resource? +

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

Can I rate-limit write_fhir_resource? +

Yes. Add a rate_limit block to the write_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 write_fhir_resource completely? +

Set action: deny in the PolicyLayer policy for write_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 write_fhir_resource? +

write_fhir_resource is provided by the MCP FHIR Server MCP server (mrosata/mcp-fhir). PolicyLayer sits as a proxy in front of this server to enforce policies before tool calls reach the server.