Methodology

Every determination is derived from the CMS Monthly Prescription Drug Plan Formulary and Pharmacy Network Information public use files. These are the formularies Medicare drug plans file with the regulator, not marketing summaries — which is why they are a stronger source than a payer’s published PDF, and why they carry a per-drug prior-authorization flag at all.

Drug names come from RxNorm, published by the U.S. National Library of Medicine.

Formulary effective

2026-06-30

Retrieved

2026-07-19

Plans

5,496

Payer brands

317

Drug products

6,128

Formulary rows

1,124,586

Source SHA-256

e626e6bcda1aa6a0071e6f0df6bafe686ae41842cdf0a9feffdc649b6d3ff3ae

Covers

• Medicare Part D outpatient prescription drug benefits
• Medicare Advantage Prescription Drug (MAPD) plans and standalone Part D (PDP) plans
• Prior authorization, step therapy and quantity limits, per drug per plan

Does not cover

• Medical or procedure prior authorization — imaging, surgery, infusions administered under the medical benefit. Those are CPT-coded and published separately by each payer.
• Commercial or employer-sponsored plans
• Medicaid, TRICARE and VA benefits
• Whether a specific member has met a plan’s criteria — only what the plan requires

We do not reproduce commercial payers’ medical prior-authorization lists. Several publish them under terms that forbid redistribution, and they embed CPT® descriptors, which are copyrighted by the American Medical Association. Where we reference such a list we link to the payer’s own document instead of copying it.

The engine is deterministic. No language model sits in the determination path, so the same input always produces the same output, and every answer is a projection of a filed formulary.

• Absence is never a green light. A drug missing from a formulary is reported as not on formulary — meaning not covered, which is generally worse for the patient than needing authorization. It is never reported as “no prior authorization required”.
• A payer is not one policy. Where requirements differ across a payer’s plans we report varies and show the split, rather than choosing one plan to speak for all of them.
• Brand answers are pessimistic in the honest direction. If one strength under a brand requires authorization and another does not, the brand-level answer is varies, never “not required”.
• Unknown means unknown. If we hold no filing for a payer, we say so. That is never evidence that authorization is unnecessary.

We publish the SHA-256 of the exact CMS file behind the corpus. Download the same file from CMS, hash it, and compare — if the hashes match, you are looking at the bytes we read. The API returns the same hash on every determination, and the MCP get_source tool returns it on demand.

API documentation · MCP server