Public API is documented

An undocumented public API surface forces every consumer to read the source to understand what a function accepts, what it returns, and when it throws. At scale this is a critical iso-25010:2011 analysability failure: every hour a developer spends reading implementation code instead of documentation is a direct tax on adoption and integration speed. The 80% coverage threshold exists because partial documentation is worse than none — it creates false confidence, leaving the undocumented 20% as silent landmines. TypeScript types alone do not satisfy this: a type signature names parameters but doesn't explain their semantics, valid ranges, or side effects.

Document every exported function with a description, parameter descriptions, and return type. Type annotations are not sufficient — add prose explaining semantics:

/**
 * Creates a configured client for the API.
 *
 * @param options.apiKey - Your API key (generate at https://example.com/keys)
 * @param options.baseUrl - Override the default API host (default: https://api.example.com)
 * @returns A client instance ready to make requests
 *
 * @example
 * const client = createClient({ apiKey: process.env.API_KEY })
 */
export function createClient(options: ClientOptions): Client

Run coverage with typedoc or jsdoc and verify at least 80% of exported symbols have prose descriptions before shipping.