Tag 22 shows the description (ISIN Number in below example) alongside the actual value (4 in the below example)
22 | SecurityIDSource | ISIN Number (4)
However, Tag 456, which uses the same dictionary as 22 https://www.onixs.biz/fix-dictionary/4.4/tagNum_456.html does not show the description, just the value (1 in the below example, when CUSIP (1) was the expected outcome)
456 | SecurityAltIDSource | 1