Look up the negotiated rates a payer attaches to a tax entity (TIN/EIN), resolved at query time through the canonical graph: TIN → provider groups (idx_tin_provider_group) → pg_sets → rates. Accepts hyphenated EINs (normalized digits-only 9). Every result carries provenance: tin_business_name (the payer-asserted entity name), tin_scope_class (fanout class), and tin_index_path ('membership' = payer-asserted NPI↔TIN rows; 'bridge' = system-level group evidence). A TIN is system-shared, NOT building-exact — use lookup_rates_for_npi first for building-specific evidence; this is the fallback rung of the facility identity ladder. Payers without a TIN index (e.g. carefirst-class, no usable EIN rows) return an honest empty. PAGED: limit (default 25, max 500) and offset bound both matching_rates and provider_groups; rate_count / provider_group_count are the full totals and paging names what was cut plus the call that returns the next page. value is a COUNT, never a price: it is the TOTAL number of matching rates, unit says so, and headline spells it out in fields (kind=count, is_a_price=false). The prices themselves are one per row in matching_rates.