In YSQL you can query the system table INFORMATION_SCHEMA.COLUMNS to list details about each of the columns in table.
Example:
yugabyte=# CREATE SCHEMA test_schema;
CREATE SCHEMA
yugabyte=# CREATE TABLE test_schema.test_table (c1 INT PRIMARY KEY, c2 VARCHAR, c3 VARCHAR(30) NOT NULL);
CREATE TABLE
yugabyte=# SELECT column_name, data_type, character_maximum_length, numeric_precision, numeric_scale
yugabyte-# FROM information_schema.columns
yugabyte-# WHERE table_schema = 'test_schema'
yugabyte-# AND table_name = 'test_table'
yugabyte-# ORDER BY ordinal_position;
column_name | data_type | character_maximum_length | numeric_precision | numeric_scale
-------------+-------------------+--------------------------+-------------------+---------------
c1 | integer | | 32 | 0
c2 | character varying | | |
c3 | character varying | 30 | |
(3 rows)
Have Fun!