The agencies I've worked actually all let me interview the dev(s) before the contract was signed. If someone didn't seem a good fit we would either get another

The agencies I've worked actually all let me interview the dev(s) before the contract was signed. If someone didn't seem a good fit we would either get another candidate or renegotiate rates. This was for augmenting an existing team though, things are different if you outsource a whole project.