AI agents call fhir.read to retrieve information from FhirMCP without modifying anything — typically the context-gathering step in research, monitoring, and reporting workflows, before the agent takes action elsewhere.
This tool retrieves healthcare data (FHIR resources) without modifying or deleting it, placing it in the Read category. However, severity is elevated to 'high' because FHIR resources contain Protected Health Information (PHI) that is subject to HIPAA and similar regulations. Unauthorized or misused data retrieval of patient records poses significant privacy and compliance risks.
From the tool's definition Tool name is 'fhir.read' and description states it 'Read[s] a specific FHIR resource by ID' with no modification or deletion mentioned. This is a retrieval operation.
Attacks that exploit this kind of access
Read a specific FHIR resource by ID with optional field selection. It is categorised as a Read tool in the FhirMCP MCP Server, which means it retrieves data without modifying state.
Register the Fhir MCP server in PolicyLayer and add a rule for fhir.read: 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 FhirMCP. Nothing to install.
fhir.read 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 fhir.read 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 fhir.read. 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.
fhir.read is provided by the Fhir MCP server (xsovx/fhir-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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