get_market_share

Get Market Share

What it answers

Returns a Medicare Advantage plan's or contract's county-level enrollment and its SHARE of the local MA market: for each county, the plan's enrollees, the county's total MA enrolled and Medicare-eligible population, the MA penetration rate, the plan's share of county MA enrollment, and the year-over-year change in the plan's county enrollment. Filter by contract_id (required) + optional plan_id (plan vs contract total), optional state (2-letter, e.g. 'FL'), and optional month ('2024-03'); defaults to the latest available month.

RETURNS an actual SHARE with the arithmetic disclosed, not a raw headcount: value.summary.share_pct is the footprint share, and it always ships alongside its numerator (share_numerator_plan_enrollees) and its denominator (share_denominator_county_ma_enrolled), so nobody has to trust a bare percentage. The denominator is the total MA enrollment of the counties this plan actually operates in for the month in scope, NOT the national MA market. value.counties is the per-county row list (plan enrollees, county MA enrolled, county eligibles, penetration, share_pct, yoy_change), largest first; value.row_counts carries matched / returned / truncated and value.query the resolved month. `limit` bounds the county list (default 200, max 2000).

This is the geography + competition lens; pair with get_enrollment for the plan/contract totals. Suppressed county cells (CMS redacts under 11) come back with null enrollees and null share, never zero, and the summary carries a [low, high] bound on the numerator that brackets them. A contract id with no county rows returns found=false with a not_found_reason.

SOURCE: CMS Monthly Enrollment by CPSC + MA State/County Penetration.

Inputs

contract_id

string · required

limit

integer · optional

month

string · optional

plan_id

string · optional

state

string · optional

Call it

From an agent: connect the Vlada MCP once (one click for Claude, ChatGPT, Cursor, VS Code) and ask in plain English; the agent selects get_market_share when the question fits. From code: the same tool over REST with an API key. The schema endpoint needs no key.

curl -X POST https://api.vladahealth.com/v1/tools/get_market_share \
  -H "Authorization: Bearer $VLADA_API_KEY" \
  -H "Content-Type: application/json" \
  -d '{"contract_id":"<contract_id>"}'

curl https://api.vladahealth.com/v1/tools/get_market_share/schema      # the JSON schema, no auth
# MCP endpoint (Streamable HTTP): https://mcp.vladahealth.com/mcp

What comes back

Typed rows plus provenance on every answer: the public source file, its vintage, the methodology, and a response_hash you can replay. Prove and replay tools turn any number into a re-runnable receipt. A number the data cannot support comes back as “not in the data”, never as zero.

Sources behind it

medicare_silver.enrollment_monthly_county
medicare_silver.ma_state_county_penetration

tables: medicare_silver.enrollment_monthly_county · medicare_silver.ma_state_county_penetration

Known limits

County cells under 11 enrollees are CMS-redacted (null enrollees, null share).
Share = plan county enrollees / total MA enrolled in county (penetration file).

As of the 2026-09-19 build of the served surface · machine-readable catalog · the live server may run a different version; the schema endpoint above is authoritative for what is deployed.