Report what diff data is available between two versions of a terminology. For most terminologies this is guidance only — the server doesn't ship historical snapshots, so the tool points at the publisher's official changelog and explains the cadence. bundled_versions lists the version(s) this serv...
Part of the Medical Terminologies MCP server.
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AI agents call terminology_diff to retrieve information from Medical Terminologies MCP without modifying any data. This is common in research, monitoring, and reporting workflows where the agent needs context before taking action. Because read operations don't change state, they are generally safe to allow without restrictions -- but you may still want rate limits to control API costs.
Even though terminology_diff only reads data, uncontrolled read access can leak sensitive information or rack up API costs. An agent caught in a retry loop could make thousands of calls per minute. A rate limit gives you a safety net without blocking legitimate use.
Read-only tools are safe to allow by default. No rate limit needed unless you want to control costs.
{
"version": "1",
"default": "deny",
"tools": {
"terminology_diff": {}
}
}See the full Medical Terminologies MCP policy for all 31 tools.
These attack patterns abuse exactly the kind of access terminology_diff gives an agent. Each links to the full case and the policy that stops it:
Other read tools across the catalogue. The same approach applies to each: allow, with a rate cap to control cost.
Report what diff data is available between two versions of a terminology. For most terminologies this is guidance only — the server doesn't ship historical snapshots, so the tool points at the publisher's official changelog and explains the cadence. bundled_versions lists the version(s) this server actually has on hand. For ICD-10 vs ICD-11 specifically, the tool surfaces a real cross-revision summary from the bundled WHO transition tables (the ICD-10 → ICD-11 case is a structural diff between two WHO revisions). Use terminology: "icd10" with no to_version to get the cross-revision summary: total mapped ICD-10 categories, how many are 1:1 vs split into multiple ICD-11 codes, and the average number of alternatives when split. Inputs: - terminology (required): which terminology to report on. - from_version (optional): the version you have data from. If omitted, the tool reports against the currently-bundled version. - to_version (optional): the version you want to compare to. If omitted, the tool reports against the publisher's latest known release. This tool is intentionally a metadata + guidance layer, not a diff engine — for terminologies that change frequently (SNOMED, LOINC, RxNorm, MeSH), the publisher's official changelog is the authoritative source.. It is categorised as a Read tool in the Medical Terminologies MCP MCP Server, which means it retrieves data without modifying state.
Register the Medical Terminologies MCP server in PolicyLayer and add a rule for terminology_diff: 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 Medical Terminologies MCP. Nothing to install.
terminology_diff 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 terminology_diff 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 terminology_diff. 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.
terminology_diff is provided by the Medical Terminologies MCP server (sidneybissoli/medical-terminologies). PolicyLayer sits as a proxy in front of this server to enforce policies before tool calls reach the server.
Deterministic rules across all 31 Medical Terminologies MCP tools. Per-identity grants. Full audit log. Live in minutes. Nothing to install.
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