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 v1.0): source, URL, data vintage, extraction instant, 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.

First observedSep 6, 2026

TDQS

A4.6/5.0

Behavior5/5

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

Beyond the readOnly/idempotent annotations, the description discloses the tool's core behavioral limitation: it does not perform the mapping, only returns guidance. It also explains the licensing constraints behind direct LOINC→SNOMED mappings, setting accurate expectations for what the tool can and cannot deliver.

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

Conciseness4/5

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

The core purpose is front-loaded in the first sentence, and the remaining paragraphs are organized logically (limitation, alternatives, input). The licensing paragraph is somewhat lengthy and overlaps with 'does not perform the mapping,' but each section earns its place for a domain-specific tool.

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?

For a single-parameter, read-only tool with an output schema, the description covers everything an agent needs: purpose, limitations, alternatives, input format, and expected type of result. No critical operational details are missing.

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?

The schema fully documents the loinc_code parameter with pattern and example, so baseline is 3. The description adds examples with semantic labels ('2339-0 (Glucose)'), but this is a minor supplement to an already well-documented parameter.

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?

The description opens with a specific verb and resource: 'looks up a LOINC code in NLM Clinical Tables and returns guidance...' It then explicitly declares 'It does not perform the mapping,' which distinguishes this tool from sibling mapping tools like map_icd10_to_icd11 and search tools.

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?

The description provides explicit when-to-use and when-not-to-use guidance, naming alternatives: 'For programmatic LOINC → SNOMED mapping, use UMLS or the LOINC Expression Association files. For interactive lookup, use the SNOMED CT browser... or RELMA.' This leaves no ambiguity about when to choose this tool.

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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