The same problem.

PG::SyntaxError: ERROR: return and sql tuple descriptions are incompatible

Incorrect description:

Some use the format "First-name Last-name" to identify a person, others use the format "Last-name, First-name".

SELECT *
  FROM prospects
 WHERE LENGTH(full_name) - LENGTH(REGEXP_REPLACE(full_name, ' ', '', 'g')) > 1

id full_name credit_limit
1 MS. BRYANA OKUNEVA 8772.04
2 MRS. ERLING LAKIN 7113.91
6 SHAINA KONOPELSKI DVM 6729.87
12 MISS SIERRA WINTHEISER 5622.56
16 STEPHANIE KUNZE SR. 8574.93
...

MS., MRS., etc. is Title and not part of Last-name or First-name.