AI agents call getEncounterById to retrieve information from Medplum MCP Server without modifying anything — typically the context-gathering step in research, monitoring, and reporting workflows, before the agent takes action elsewhere.
This tool retrieves existing healthcare data (encounter records) without modifying, deleting, or executing external operations. It is a pure read operation on a FHIR server. The blast radius of misuse is minimal—an AI agent could access encounter data it shouldn't, but cannot modify or delete records, and no irreversible actions are possible.
From the tool's definition Tool name 'getEncounterById' and description 'Retrieves an encounter by its unique ID' indicate a query operation with no side effects.
Documented attack patterns abuse exactly the kind of access getEncounterById gives an agent:
PolicyLayer is an MCP gateway — it sits between your AI agents and Medplum MCP Server, and nothing reaches the server without passing your rules. This is the rule we recommend for getEncounterById:
{
"version": "1",
"default": "deny",
"tools": {
"getEncounterById": {}
}
} getEncounterById is read-only, so it stays allowed — but everything else on the server is denied unless you say otherwise.
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Retrieves an encounter by its unique ID. It is categorised as a Read tool in the Medplum MCP Server MCP Server, which means it retrieves data without modifying state.
Register the Medplum MCP Server MCP server in PolicyLayer and add a rule for getEncounterById: 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 Medplum MCP Server. Nothing to install.
getEncounterById 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 getEncounterById 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 getEncounterById. 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.
getEncounterById is provided by the Medplum MCP Server MCP server (rkirkendall/medplum-mcp). PolicyLayer sits as a proxy in front of this server to enforce policies before tool calls reach the server.
Start from Medplum MCP Server, add the rest of your stack, and see everything your agents can call. Then put policy on all of it.
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37 Medplum MCP Server tools catalogued and risk-classified — across an index of 43,000+ MCP servers.