The static operation uses Velocity Template Language (VTL), which is quite a powerful tool in extending the functionality of your transforms. This means you can use standard Java functions on data types like strings. In your case, returning the length of a string attribute is as simple as the following transform:
{
"attributes": {
"name": {
"attributes": {
"attributeName": "name",
"sourceName": "Employees"
},
"type": "accountAttribute"
},
"value": "$name.length()"
},
"name": "Attribute Length",
"type": "static"
}
input: adam.archer
output: 11