system.functions
Contains information about scalar, aggregate and user defined functions.
mysql> SELECT * FROM system.functions limit 10;
+------------------+------------+--------------+------------+-------------+
| name | is_builtin | is_aggregate | definition | description |
+------------------+------------+--------------+------------+-------------+
| format | 1 | 0 | | |
| todatetime32 | 1 | 0 | | |
| quote | 1 | 0 | | |
| blake3 | 1 | 0 | | |
| subtractmonths | 1 | 0 | | |
| like | 1 | 0 | | |
| right | 1 | 0 | | |
| toyyyymmddhhmmss | 1 | 0 | | |
| abs | 1 | 0 | | |
| sign | 1 | 0 | | |
+------------------+------------+--------------+------------+-------------+