Required, as-prescribed and optional: what R, A and O actually mean
The three codes in the FAR matrix are not degrees of the same thing. They point to three different decision rules.
When a checklist says a clause is required, teams treat it as settled and move on. The FAR matrix does not work that way, and misreading its three codes is the most common error a new compliance lead makes.
Required (R) is the closest to a plain instruction: for this contract type, the clause belongs in the contract. Even here the prescription can add a condition, so R is a strong default rather than an absolute. As prescribed (A) is the code people get wrong. It deliberately delegates the decision to the prescription in the clause's FAR part. The matrix is saying: this clause is available and appropriate for this contract type when the facts set out in its prescription are present. The facts might be a dollar threshold, a place of performance, a funding source, a type of work, or something about the contractor. Until you read the prescription, you do not know whether A applies to your award.
Optional (O) is the most permissive. The clause is available for the contract type, and whether to use it is largely a matter of the contracting officer's judgement and the needs of the acquisition. An optional clause is not an invitation to add terms; it is a tool available to the office.
The practical consequence is that counting the cells in a column tells you almost nothing. A column with three hundred A marks is not three hundred obligations; it is three hundred clauses, each gated by its own prescription. The work lives in the prescriptions, and that is exactly why MyFCExperts links every clause to the eCFR section where its prescription is stated, and shows the prescription number beside the title.
Read the codes as questions rather than answers. R asks whether a special condition applies. A asks whether the facts in the prescription are present. O asks whether the office wants the clause. None of the three is a determination about your contract, and MyFCExperts never presents it as one.