Obtain an API key from the CMS developer portal at developer.cms.gov; the Marketplace API powers HealthCare.gov's Plan Compare and Window Shop tools
POST to the /plans/search endpoint with a JSON body containing household income, household members (each with age, tobacco use, and relationship), and the applicant's zip code and county FIPS code to receive plan-year-appropriate results
Parse the returned plans array; each plan object includes premium (before and after APTC subsidy), metal level, deductible, MOOP (maximum out-of-pocket), and network type (HMO, PPO, etc.)
Apply the estimated APTC (advanced premium tax credit) returned in the response to compute the net monthly premium the consumer would pay; surface the subsidy amount separately for transparency
Filter and sort plans by the consumer's priority (lowest premium, lowest deductible, or preferred metal level) and present a comparison table before linking to HealthCare.gov for enrollment
Known gotchas
The Marketplace API serves only the 30 states using the HealthCare.gov platform; state-based exchanges (e.g., California Covered, New York State of Health) have separate APIs or no public API
County FIPS code is required in addition to zip code because zip codes can span multiple counties and rating areas; an incorrect FIPS code will return plans for the wrong rating area
Plan data is updated during open enrollment and during special enrollment periods; cache responses for no longer than 24 hours and invalidate on plan-year boundaries
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claude mcp add --transport http waymark https://mcp.waymark.network/mcp