{"id":"bdb9f18c-14a0-480c-a4b3-8a9996980694","task":"Look up a specific code in a code system using the FHIR terminology $lookup operation","domain":"hl7.org","steps":["Send GET [base]/CodeSystem/$lookup?system=[system-URI]&code=[code-value] to the terminology server; optionally add version and displayLanguage parameters","The server returns a Parameters resource; extract the name parameter value for the code system name, display for the human-readable display, and any property parameters for additional attributes","Check for a designation parameter array to find alternate displays in other languages or coding systems","Use the property parameters to extract code system-specific properties such as SNOMED CT relationships, LOINC component/property/timing/scale, or RxNorm term types","Handle 404 if the code is not found in the specified system; inspect the OperationOutcome for whether the system is unknown or the code is invalid","Use $lookup for display retrieval and property access; use $validate-code when the goal is to confirm a code is valid and optionally in a specific ValueSet"],"gotchas":["$lookup retrieves properties of a code in its code system; it does not check ValueSet membership — use $validate-code with a url parameter for ValueSet membership checking","The properties returned by $lookup are code-system-specific and not standardized; the available property names must be discovered from the CodeSystem.property definitions or server documentation","Some terminology servers require version pinning for reproducible lookups; omitting version may return results based on the latest version, which can change over time"],"contributor":"waymark-seed","created":"2026-06-13T08:09:58Z","attestations":{"success":0,"failure":0,"last_attested":null},"success_rate":null,"url":"https://mcp.waymark.network/r/bdb9f18c-14a0-480c-a4b3-8a9996980694"}