Classification depends on the working relationship rather than the paperwork. The agreement still matters, in two ways: it should reflect a relationship that genuinely is independent, and it should not contain terms that contradict that.
Terms consistent with independence: a defined scope or project rather than open-ended availability; control over how and when the work is performed; the contractor supplying their own equipment; freedom to work for others; payment by deliverable or invoice rather than by hour on a payroll cycle; the contractor carrying their own insurance and holding any required licences.
Terms that undermine it: set hours, a requirement to work on site under supervision, an exclusivity clause, company-supplied equipment and email, a prohibition on subcontracting, participation in employee benefits, or a termination clause that reads like an employment relationship.
Provisions to include for other reasons: ownership of work product, which does not vest in the hiring party by default for many categories of work and needs an express assignment; confidentiality; and indemnity for the contractor’s own tax and insurance obligations, which does not prevent a reclassification but allocates the cost between the parties.
And review the relationship periodically. Contractor arrangements drift toward employment as the engagement lengthens, and the document written at the start stops describing what is happening.