mcp-terminology

Unified LOINC / SNOMED CT / RxNorm / ICD-10 MCP server — v1.0.0 Part of the fhir-mcp-suite monorepo.

Query four major clinical terminology systems through a single MCP server backed by the free public FHIR R4 terminology server (tx.fhir.org/r4).

Tools

Supported systems for lookup_code

Quick start

# Install into the monorepo workspace
uv sync --all-packages

# Run (stdio mode — for Claude Desktop)
uv run mcp-terminology

# Run with SSE transport (port 8001)
MCP_TRANSPORT=sse uv run mcp-terminology

Claude Desktop configuration

{
  "mcpServers": {
    "terminology": {
      "command": "uv",
      "args": [
        "--directory",
        "/path/to/fhir-mcp-suite",
        "run",
        "mcp-terminology"
      ],
      "env": {
        "TERMINOLOGY_BASE_URL": "https://tx.fhir.org/r4",
        "LOG_LEVEL": "WARNING"
      }
    }
  }
}

Example tool calls

Look up a LOINC code

{ "system": "loinc", "code": "8302-2" }

{
  "system_url": "http://loinc.org",
  "system_name": "LOINC",
  "code": "8302-2",
  "display": "Body height",
  "definition": "...",
  "designations": [...],
  "version": "2.78"
}

Translate SNOMED → ICD-10-CM

{
  "code": "73211009",
  "source_system": "snomed",
  "target_system": "icd-10-cm"
}

Expand a ValueSet

{ "url": "http://hl7.org/fhir/ValueSet/administrative-gender" }

Architecture

Claude Desktop / LangGraph agent
         │  MCP stdio
    mcp-terminology (this package)
         │  HTTPS
    tx.fhir.org/r4  (free public FHIR R4 terminology server)
         └── CodeSystem/$lookup
         └── ValueSet/$expand
         └── ConceptMap/$translate

Observability: every tool call is traced in LangFuse (input, output, latency, response bytes). Set LANGFUSE_PUBLIC_KEY / LANGFUSE_SECRET_KEY / LANGFUSE_HOST to enable.

Eval results

mcp-terminology eval — 21 golden cases
  Error/security cases: 6/6   100%  (network-independent)
  Integration cases:    run with `--tags lookup search translate expand`
  CI threshold:         85% pass rate

Run locally:

# Error cases only (no network needed):
uv run python evals/mcp-terminology/run_eval.py --tags error

# Full suite (requires tx.fhir.org):
uv run python evals/mcp-terminology/run_eval.py

# CI gate:
uv run python evals/mcp-terminology/run_eval.py --ci --threshold 0.85

Security

• Input sanitization on all parameters (regex allowlist on codes, http/https-only URLs, control-char stripping on filters)
• Hard cap of 100 results per query
• No PHI — uses only synthetic/public code lookups
• See validation.py for the full allowlist

License

Apache-2.0 — see LICENSE.