The Problem
Prior authorization costs US clinicians 12 hours per week and delays patient care. $35B in annual administrative waste. The CMS Interoperability Final Rule (CMS-0057-F) mandates automation by 2027 — but most systems still run on faxes.
What It Does
Prior Auth Copilot is an A2A agent on Prompt Opinion that automates the full prior authorization workflow end-to-end:
- Checks PA requirement — Is PA needed for this CPT code + payer? (Da Vinci CRD)
- Retrieves medical-necessity criteria — structured payer policy rules (Da Vinci DTR)
- Pulls FHIR chart — conditions, observations, medications via Prompt Opinion's FHIR MCP
- Matches evidence with GenAI — evaluates each criterion against the chart, cites specific FHIR resource IDs. Hallucinated citations are automatically stripped.
- Generates the PA packet — justification letter + FHIR Claim bundle + pre-drafted appeal letter (Da Vinci PAS)
Every packet is flagged requires_human_review: true. The clinician approves. No autonomous submissions.
How We Built It
Two artifacts composed on Prompt Opinion:
PA Criteria MCP Server — Python FastMCP server, SHARP-on-MCP compliant, deployed on Hugging Face Spaces. Accepts X-FHIR-Server-URL, X-FHIR-Access-Token, X-Patient-ID headers. Uses Claude Haiku for evidence matching and letter generation. Four tools:
| Tool | Da Vinci Phase | Purpose |
|---|---|---|
check_pa_requirement |
CRD | Is PA required? |
get_policy_criteria |
DTR | Structured criteria |
match_clinical_evidence |
DTR | GenAI grounded matching |
generate_pa_packet |
PAS | Full submission packet |
Prior Auth Copilot A2A Agent — configured in Prompt Opinion, connected to the default FHIR MCP + our PA Criteria MCP. Agent Card advertises 4 skills: PriorAuthCheck, EvidenceGathering, PAPacketGeneration, AppealDrafting — so other agents can delegate to it.
Safety Architecture
- Evidence grounding: LLM claims without valid FHIR citations are auto-rejected (status:
ungrounded) - PHI guardrail: regex check on every LLM output before it leaves the server
- FHIR domain allowlist: only known synthetic test servers accepted
- SHA-256 hash-chained audit log on every tool call
- Human-in-the-loop: enforced in agent prompt and packet metadata
Standards Compliance
- HL7 FHIR R4
- SHARP-on-MCP (Prompt Opinion context propagation)
- Da Vinci CRD / DTR / PAS
- CMS-0057-F Interoperability and Prior Authorization Final Rule
Challenges
- Grounding LLM evidence to actual FHIR resources (solved with post-call citation validator)
- Keeping end-to-end latency under 60 seconds across FHIR + LLM calls (solved with parallel fetches and capped token budgets)
- Modeling payer-specific criteria variance for same CPT code (solved with payer-indexed criteria schema)
What's Next
- Expand from 5 procedures to 50
- CDS Hooks integration for EHR order-entry trigger
- Partner with real payer FHIR sandbox (Humana, CMS Blue Button)
- Appeals orchestrator sub-agent delegating via A2A
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