Example deploy using vercel token (.circleci/config.yml and .now/linkproject.sh)

config.yml

defaults: &defaults
    docker:
        - image: circleci/node:12.14
    working_directory: ~/tmp/circleci-now

version: 2
jobs:
    checkout:
        <<: *defaults
        steps:
            - checkout
            - attach_workspace:
                at: ~/tmp/circleci-now
            - restore_cache:
                keys:
                    - npm-cache-{{ .Branch }}-{{ checksum "package.json" }}
                    - npm-cache-{{ .Branch }}
                    - npm-cache-
            - run:
                name: NPM Install
                command: npm install
            - save_cache:
                key: npm-cache-{{ .Branch }}-{{ checksum "package.json" }}
                paths:
                    - node_modules
            - persist_to_workspace:
                root: .
                paths: .
    
    unit-test:
        <<: *defaults
        steps:
            - attach_workspace:
                at: ~/tmp/circleci-now
            - run:
                name: NPM Install
                command: npm install
            - run:
                name: Unit Test with Code Coverage
                command: |
                  curl -L https://codeclimate.com/downloads/test-reporter/test-reporter-latest-linux-amd64 > ./cc-test-reporter
                  chmod +x ./cc-test-reporter
                  ./cc-test-reporter before-build
                  npm run test:coverage
                  ./cc-test-reporter after-build -t lcov -r ${TEST_REPORTER_ID}
    
    deploy:
        <<: *defaults
        steps:
            - attach_workspace:
                at: ~/tmp/circleci-now
            - run:
                name: Deploy
                command: |
                  ./.now/linkproject.sh
                  if [ "${CIRCLE_BRANCH}" == "master" ];
                  then
                    npx now --token $ZEIT_TOKEN --scope $ZEIT_ORG_ID --confirm --prod
                  else
                    npx now --token $ZEIT_TOKEN --scope $ZEIT_ORG_ID --confirm
                  fi
                  
workflows:
    version: 2
    test-deploy-purge:
        jobs:
            - checkout
            - unit-test:
                requires:
                    - checkout
            - deploy:
                filters:
                  branches:
                    only:
                      - develop
                      - master
                requires:
                    - unit-test

linkproject.sh

#!/bin/bash
set -e

JSON=$(cat <<-EOF
{
    "orgId": "$ZEIT_ORG_ID",
    "projectId": "$ZEIT_PROJECT_ID"
}
EOF
)

echo $JSON > .now/project.json

Thanks for your snippet. I just found out that you just can provide the org and project id via environment variables entirely: VERCEL_ORG_ID and VERCEL_PROJECT_ID.

Then there is no need for creating the project.json