How a job role is defined
The job description: what the hiring manager thinks they want.
The candidate sees it, says, "I could do that".
The candidate manages to get an interview. The interviews go well.
The hiring manager says, "I want to hire this person (even though they're not quite an exact match for the job description)".
The deal gets done.
The candidate starts.
The job description is forgotten.
The role becomes what the candidate wants it to be.
Reality rarely matches a hiring manager's initial job description.
In any role, the candidate will shape the job role as much as the job role shapes the candidate. We are all strangely unique individuals and what we bring to work every day (our skills, our interest, our knowledge, our biases, our energy, our network, our values, our motivations) turns a job description into reality. There will be things in the original job description that we don't do, there will be other things we can do and want to do which are not in the job description.
Reality rarely matches the job description and this is especially the case for startups. This is because as much as you try and write a job description that matches what you think you need in your team now, that will change within 6 months in a startup - things move very fast.
Instead of asking, "will this candidate meet my job description?", try instead asking, "if this candidate could create their ideal job, what would it be?"
If that ideal job of theirs sounds like the kind of challenge you could offer, now and into the future, you might just have found a great match. A job description therefore is an advert to attract great people, it's marketing.
Who you hire will determine what actually gets done.