The fields and filters objects work differently than documented.

[patcain]

if i do a POST /api/v1/cryptocurrency-addresses with a body of
{
"fields": [ "id" ]
}
I get an error:
{
"type": "invalid_request_error",
"code": "validation_failed",
"message": "The 'source' field is required (and 7 more errors)",
"errors": {
"source": [
"The 'source' field is required"
] }

This seems odd.

[patcain]

This is a documentation error. Each eCX module has FIVE endpoints. Get/Get{id}/POST/Put{id} ... and ... search. The search endpoint is where one does all the filtering.