Medical Terminologies MCP

Map LOINC to SNOMED CT (Guidance)

map_loinc_to_snomed

Read-onlyIdempotent

This tool looks up a LOINC code in NLM Clinical Tables and returns guidance on where to obtain a LOINC → SNOMED CT mapping. It does not perform the mapping.

Direct LOINC → SNOMED CT mappings are not freely available via API. UMLS Metathesaurus contains the relationships but requires an individual UMLS Terminology Services license; the LOINC SNOMED CT Expression Association is published by Regenstrief Institute as part of the LOINC release and requires authenticated download from loinc.org under the LOINC license.

For programmatic LOINC → SNOMED mapping, use UMLS or the LOINC Expression Association files. For interactive lookup, use the SNOMED CT browser available to your organization or the Regenstrief RELMA desktop tool.

Provide a LOINC code like "2339-0" (Glucose) or "718-7" (Hemoglobin).

Input Schema

TableJSON Schema

Name	Required	Description	Default
`loinc_code`	Yes	LOINC code (e.g., 2339-0 for Glucose)

Output Schema

TableJSON Schema

Name	Required	Description
`status`	Yes	Always "guidance-only" — direct LOINC → SNOMED CT mappings require licensed sources (UMLS Metathesaurus or LOINC SNOMED CT Expression Association). This tool returns pointers, not the mapping itself.
`guidance`	Yes	Short human-readable explanation of why this tool returns guidance instead of a mapping.
`loinc_code`	Yes	The LOINC code as submitted.
`provenance`	Yes	Provenance block (contract v1.1): source, URL, data vintage, extraction instant, origin diagnostics, citation, license
`attribution`	Yes	Canonical source URLs of this response (attribution list)
`loinc_details`	Yes	NLM Clinical Tables details for the LOINC code (component, system, property, etc.). Null when the code was not found upstream.
`mapping_sources`	Yes	Structured list of authoritative LOINC → SNOMED CT mapping sources (UMLS Metathesaurus, LOINC SNOMED CT Expression Association, Regenstrief RELMA).

Schema Changelog

Changes observed during successful MCP inspections.

Changed3 schema fields changedSep 27, 2026

changedOutput schema / properties / provenance / description

Previous value: -"Provenance block (contract v1.0): source, URL, data vintage, extraction instant, citation, license"New value: +"Provenance block (contract v1.1): source, URL, data vintage, extraction instant, origin diagnostics, citation, license"

addedOutput schema / properties / provenance / properties / retrieval

Added value: +{
+  "anyOf": [
+    {
+      "additionalProperties": false,
+      "properties": {
+        "anomalies": {
+          "description": "Anomalias superadas até o sucesso, somadas por classe, em ordem fixa; [] se nenhuma",
+          "items": {
+            "additionalProperties": false,
+            "properties": {
+              "count": {
+                "description": "Ocorrências desta classe na chamada",
+                "maximum": 9007199254740991,
+                "minimum": 1,
+                "type": "integer"
+              },
+              "kind": {
+                "description": "Classe da anomalia (vocabulário fechado do contrato)",
+                "enum": [
+                  "timeout",
+                  "network",
+                  "http_4xx",
+                  "http_5xx",
+                  "rate_limited",
+                  "malformed_body"
+                ],
+                "type": "string"
+              }
+            },
+            "required": [
+              "kind",
+              "count"
+            ],
+            "type": "object"
+          },
+          "type": "array"
+        },
+        "attempts": {
+          "description": "Tentativas somadas, incluindo as repetidas (>= requests)",
+          "maximum": 9007199254740991,
+          "minimum": 1,
+          "type": "integer"
+        },
+        "requests": {
+          "description": "Idas distintas à origem que compõem esta resposta (fatias, páginas)",
+          "maximum": 9007199254740991,
+          "minimum": 1,
+          "type": "integer"
+        },
+        "unstable": {
+          "description": "true se houve repetição (attempts > requests) ou alguma anomalia",
+          "type": "boolean"
+        }
+      },
+      "required": [
+        "requests",
+        "attempts",
+        "anomalies",
+        "unstable"
+      ],
+      "type": "object"
+    },
+    {
+      "type": "null"
+    }
+  ],
+  "description": "Origin diagnostics of THIS source in this call (contract v1.1): requests made to the upstream, attempts summed across retries, anomalies worked around (kind + count); unstable=true when any anomaly happened. null when nothing was measured (bundled dataset, or response served entirely from cache)"
+}

changedOutput schema / properties / provenance / required

Previous value: -[
-  "source",
-  "source_url",
-  "data_vintage",
-  "retrieved_at",
-  "citation",
-  "license"
-]New value: +[
+  "source",
+  "source_url",
+  "data_vintage",
+  "retrieved_at",
+  "retrieval",
+  "citation",
+  "license"
+]

Changed1 schema field changedSep 11, 2026
- addedInput schema / additionalProperties
```
Added value: +false
```
First observedSep 6, 2026

TDQS

A4.5/5.0

Behavior4/5

Does the description disclose side effects, auth requirements, rate limits, or destructive behavior?

Annotations already declare readOnly/idempotent/openWorld/non-destructive, so safety is covered. The description adds the most important behavioral fact beyond annotations: it only returns guidance and performs no mapping, plus the licensing constraints that explain why. It stops short of describing what the guidance response actually contains, but the output schema covers returns.

Agents need to know what a tool does to the world before calling it. Descriptions should go beyond structured annotations to explain consequences.

Conciseness5/5

Is the description appropriately sized, front-loaded, and free of redundancy?

Front-loaded with the critical caveat ('does not perform the mapping') before the rationale and alternatives. Every paragraph earns its place by preventing a likely mis-invocation, and it closes with the accepted input format.

Shorter descriptions cost fewer tokens and are easier for agents to parse. Every sentence should earn its place.

Completeness5/5

Given the tool's complexity, does the description cover enough for an agent to succeed on first attempt?

An output schema exists, so return values need no explanation. The description covers the one thing an agent could get wrong (assuming this performs a mapping), explains prerequisites, and points to real alternatives — everything needed to call it correctly.

Complex tools with many parameters or behaviors need more documentation. Simple tools need less. This dimension scales expectations accordingly.

Parameters3/5

Does the description clarify parameter syntax, constraints, interactions, or defaults beyond what the schema provides?

Schema coverage is 100% with a regex pattern and an example, so the schema already documents the single parameter. The description repeats the format and adds a second example ('718-7'), which is marginal value over the schema. Baseline 3 is appropriate.

Input schemas describe structure but not intent. Descriptions should explain non-obvious parameter relationships and valid value ranges.

Purpose5/5

Does the description clearly state what the tool does and how it differs from similar tools?

States a specific verb (looks up) and resource (LOINC code in NLM Clinical Tables), then crucially clarifies what it does NOT do: 'It does not perform the mapping.' This distinguishes it from genuine mapping siblings like map_icd10_to_icd11, so an agent cannot confuse the two.

Agents choose between tools based on descriptions. A clear purpose with a specific verb and resource helps agents select the right tool.

Usage Guidelines5/5

Does the description explain when to use this tool, when not to, or what alternatives exist?

Gives explicit routing: use UMLS or the LOINC Expression Association files for programmatic mapping, and the SNOMED CT browser or RELMA for interactive lookup. Also states the licensing/prerequisite condition (UMLS license, authenticated loinc.org download), so usage conditions are fully specified.

Agents often have multiple tools that could apply. Explicit usage guidance like "use X instead of Y when Z" prevents misuse.

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