This schema validator is built using Json.NET Schema and C#.

public class JsonSchemaController : ControllerBase
{
    [HttpPost]
    [Route("api/jsonschema/validate")]
    public ValidateResponse Validate(ValidateRequest request)
    {
        // Load schema
        JSchema schema = JSchema.Parse(request.Schema);
        JToken json = JToken.Parse(request.Json);

        // Validate json
        IList<ValidationError> errors;
        bool valid = json.IsValid(schema, out errors);

        // Return error messages and line info to the browser
        return new ValidateResponse
        {
            Valid = valid,
            Errors = errors
        };
    }
}

public class ValidateRequest
{
    public string Json { get; set; }
    public string Schema { get; set; }
}

public class ValidateResponse
{
    public bool Valid { get; set; }
    public IList<ValidationError> Errors { get; set; }
}

Get Json.NET Schema

Get Json.NET Schema from NuGet (recommended) or download a ZIP of the assemblies and source code: Json.NET Schema

PM> Install-Package Newtonsoft.Json.Schema