If a landlord or leasing agent simply tells you the terms, ask for something showing the terms in writing before you submit a counteroffer. If they are reluctant to offer a letter, ask for an email or a copy of the listing for the space (which will contain at least the basic leasing information).
Why is it so important to have initial terms in writing? A leasing agent acts on behalf of the interests of the landlord. If an agent either misunderstood or attempted in any way to alter the landlord’s directions, having terms in writing can show you a landlord that your counter offer was made in good faith based on information from the leasing agent.