Use the FHIR $cql operation on cqf-ruler to evaluate a named CQL expression against a patient and debug measure population logic

Steps

1. Ensure cqf-ruler is running with the clinical-reasoning module enabled; confirm the /cql/evaluate or /$cql endpoint is available via the server's CapabilityStatement or documentation
2. POST /$cql with a Parameters resource: include a subject parameter (Patient/{id}), a library parameter referencing the Library canonical URL, and an expression parameter naming the CQL expression to evaluate (e.g., 'Numerator')
3. Parse the returned Parameters resource; each result.name corresponds to an expression name and result.value holds the evaluated output (true/false for population criteria, resource lists for retrieve expressions)
4. If the expression returns unexpected results, add intermediate expression names (e.g., the retrieve expression listing qualifying diagnoses) as additional expression parameters to inspect intermediate values
5. Repeat with different patient IDs to validate that the CQL logic correctly includes and excludes patients based on their clinical data