AI agents call fhir.capabilities 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 queries and returns information about FHIR server capabilities and supported operations. It is a read-only informational operation with no side effects—it retrieves metadata about the server rather than accessing patient data or triggering external actions.
From the tool's definition Tool name 'fhir.capabilities' and description 'Get FHIR server capabilities and supported operations' indicate a retrieval operation with no data modification.
Attacks that exploit this kind of access
Get FHIR server capabilities and supported operations. 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.capabilities: 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.capabilities 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.capabilities 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.capabilities. 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.capabilities 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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