Is it JSON or not?

The following is formatted in JSON

["wclass",
{"student":{"name":"Linda Jones","legacySkill":"Access, VB 5.0"}etc..
},
{  "student":{"name":"Adam Davidson","legacySkill":"Cobol, MainFrame"}
},
{"student":{"name":"Charles Boyer","legacySkill":"HTML, XML"}
}]
This is a valid JSON according to RFC 4627.

json_01

However when you use this in SQL Server to look at the JSON using the OpenJSON, for example, you will get this error:

json_00

The reason for this error:
Msg 103, Level 15, State 4, Line 2
The identifier that starts with "wclass"...
lies in the fact that SQL Server string starts with a single quote and therefore you need to provide this declaration:

declare @json nvarchar(Max)
set @json=
'["wclass",
{"student":{"name":"Linda Jones","legacySkill":"Access, VB 5.0"}
},
{"student":{"name":"Adam Davidson","legacySkill":"Cobol, MainFrame"}
},
{"student":{"name":"Charles Boyer","legacySkill":"HTML, XML"}
}]'

When you do this the error goes away as shown:

json_02

The character count in @json is also important as you see in this SQL query:

json_03

The answer is that RFC 4627 validation requires a string to start with a double quote("), but the SQL Server's JSON validation requires the JSON to begin with a single quote(') as we saw in this post.

Is there a JSON validator in SQL Server?

Sure there is if you are using SQL Server 2016.

The Transact-SQL IsJSON() tests whether a expression(string) is JSON valid. If it is valid you should get a 1 as return value, a zero(0) if it is not valid and a null if the expression is null.

How do you use it?

This is a json string, a very simple one:
=================
{"wclass":{"student":["jay", "john", "sam"]}}
====================
The following code snippet shows how you may use it:
===========
declare @json nvarchar(150)SET @json=N'{"wclass":{"student":["jay", "john", "sam"]}}';
Select ISJSON(@json)
==========
When you run this in the SQL Server 2016 query pane, you get the return value 1 (see image below).