Apollo GraphQl Backend using Fetch API mutation

Question

I am running an apollo graphql backend and vanilla javascript fetch API in front-end it is running in chrome extension the Query works fine but the Mutation doesn't work and is returning a 400 error I am running this in Chrome extension and the query in there works

    fetch('https://dev.api.sharpstudy.io/graphql', {
        method: 'POST',
        headers: {
            authorization: `Bearer ${token}`,
            'Content-Type': 'application/json',
            Accept: "application/json, text/plain"

        },
        body: JSON.stringify({
            query: `
            mutation createBrowserTab {
                    createBrowserTab (userId: ${userId}, tabName: ${title}, tabDescription: ${title}, tabUrl:${url}, subjectId: ${subId}){
                      SavedBrowserTab {
                        tabId
                        tabUrl
                        tabName
                        tabDescription
                        subjectId
                        userId
                      }
                      message
                    } 
                  }
      `,
            // variables: {
            //     userId: userId,
            //     title: title,
            //     url: url,
            //     subId: subId


            // },
        }),
    })
        .then((res) => res.json())
        .then((result) => console.log(result));