Working knowledge of one language in your stack, such as JavaScript
Reading and reasoning about existing code
Investigating problems methodically rather than guessing
Asking clear questions and responding well to code review
Nice to have (mention, but do not screen on these):
Experience with your framework or cloud platform
Personal or open-source projects
Testing or version control experience in a team
Keep the must-have list short. Every extra requirement removes candidates, and requirements that are not needed for the work can screen out good junior developers unfairly. If a skill can be learned in the first few weeks, it belongs under nice to have.
What the team builds, the stack, the typical work, how pairing and code review work, the support in the first months, hours and pay, and the hiring process. Say how long any coding task takes.