Unable to assign value to workflow variable !!!

Hi all,

I am unable to assign a url to a workflow variable.I created a variable MasterUrl of string type in the workflow.To this I am assigning the below rest url.

[%Workflow Context:Current Site URL%]/_api/web/Lists/GetbyTitle('Product%20List')/items?$select=Person1Id,Person2Id,Product,Code, Country&expand=Person1/Id,Person2/Id&$filter=((Person1/Id%20eq%201)%20and%20(Person2/Id%20eq%2023))

What I am trying to do is filter Product List by Person1 whose userid=1 and Person2 whose userid=23 where Person1 and Person2 are Person Or Group column.

When I assign the same to the workflow and log it, the workflow does not execute.
When I clicked on the individual list item and clicked on the workflow activity icon, I can see

Retrying last request. Next attempt scheduled in less than one minute. Details of last request:
HTTP InternalServerError to http://<servername>:<port>/sites/contoso/_vti_bin/client.svc/web/lists(guid'786b572a-7bd9-4765-bcf7-f15a537fc704')/Items
Correlation Id: 903d19dc-7975-4fdf-89e5-f8ca9b7cca6b Instance Id: 1af22e59-67ed-4678-a67b-76e7d469c93f


RequestorId: 567aae7d-b65b-39b6-59a6-657026dd295f. Details: System.ApplicationException: HTTP 500 {"Transfer-Encoding":["chunked"],"X-SharePointHealthScore":["0"],"SPClientServiceRequestDuration":["586"],"SPRequestGuid":["0ee68d25-7589-4ae2-ac82-a6c96334c479"],"request-id":["0ee68d25-7589-4ae2-ac82-a6c96334c479"],"X-FRAME-OPTIONS":["SAMEORIGIN"],"MicrosoftSharePointTeamServices":["15.0.0.4641"],"X-Content-Type-Options":["nosniff"],"X-MS-InvokeApp":["1; RequireReadOnly"],"Cache-Control":["max-age=0, private"],"Date":["Wed, 30 Dec 2015 08:39:25 GMT"],"Server":["Microsoft-IIS\/7.5"],"X-AspNet-Version":["4.0.30319"],"X-Powered-By":["ASP.NET"]}
at Microsoft.Activities.Hosting.Runtime.Subroutine.SubroutineChild.Execute(CodeActivityContext context)
at System.Activities.CodeActivity.InternalExecute(ActivityInstance instance, ActivityExecutor executor, BookmarkManager bookmarkManager)
at System.Activities.Runtime.ActivityExecutor.ExecuteActivityWorkItem.ExecuteBody(ActivityExecutor executor, BookmarkManager bookmarkManager, Location resultLocation) 

When I check the ULS logs, there is nothing noteworthy with respect to workflow and the entries corresponsd to userprofile,wcf calls

When I put the same url in browser, after replacing Workflow context url variable with proper url, I am able to get the filtered values as needed.However, when I trim the url and assign only till

[%Workflow Context:Current Site URL%]/_api/web/Lists/GetbyTitle('Product%20List')/items?$select=Person1Id,Person2Id,Product,Code, Country&expand=Person1/Id,Person2/Id&$filter=Person

to the variable, the workflow works, variable is assigned and I am able to log it. But the moment, I add the / , it throws above error.

[%Workflow Context:Current Site URL%]/_api/web/Lists/GetbyTitle('Product%20List')/items?$select=Person1Id,Person2Id,Product,Code, Country&expand=Person1/Id,Person2/Id&$filter=Person1/Id

Above url ,throws error. I tried assigning them to two different variables and then linking them. No use.
I tried to log them as string,plain text,description text instead of url type. No use.

Kindly help.