Graph lane: labelled relationship EDGES between companies/entities (ownership, operates, supplies, …) — the PRODUCT (edges with tiers + provenance), named for the capability, not the meter. Typed query params (GET /relationships): the answer is about ONE entity (GreenlandAI 2026-10-01). entity_type ("company" | "infrastructure" | "deposit" | "project") + entity_id pin the START NODE; or entity — the one entity whose name equals it (case-insensitive), else the one whose name contains it. If several entities match, the call fails (isError, upstream_status 409, nothing charged) with upstream_body.detail = {error: "ambiguous_entity", candidates: [{entity_type, entity_id, name, country}], how_to_choose} — call again with entity_type + entity_id from one of them; each candidate carries has_site (true = it holds a site, so the measurement routes can answer about it; false = name-only or a country centre, which those routes refuse). The answer's resolved names the entity it is about, with its place block; every entity in the answer has one in places (rows point there by subject_ref / object_ref): has_site, height_class (its last measurement's, else unknown), last_measured, and the measurement routes filled in for it. WHEN NOT TO CALL: "did the site change" is entity_change; a volume is never in this answer (only entity_change's repeat_surface measures a volume change). hops (traversal DEPTH 1-10, default 1 — the BILLING UNIT: metered per hop, which is why billing_quote takes hops=), relation_type (one relation label, e.g. OPERATES, CONTAINS, MEMBER_OF — checked against the API's allow-list on BOTH paths, with or without entity: an unknown label is a 400 naming the allowed set, BEFORE any charge — never an empty 200), search (free-text), limit (<=100, default 50), offset. Metered — debited from the CALLING agent's own wallet, not the owner's (read it with the joules_balance tool). For the exact per-caller price before you call, use the billing_quote tool (free, tier-aware; returns joules_all_in) or check affordability with the joules_deficit tool; the true debit is the base joule_cost plus a 0.5% rail surcharge rounded up (a 100 J call debits 101 J) = joules_all_in. Preserves source_tier/tier_label on each edge — do not strip them. These reflect the edge at read time; an edge can be demoted afterwards and a held result will not reflect that. ⚠ CHARGING: the meter RESERVES before the query runs and SETTLES after delivery for what was actually delivered (an empty result settles to 0; a partial traversal settles for the hops delivered; a 4xx releases the reservation). An abandoned or timed-out call still settles once the backend delivers. A replay is served free only for the SAME credential + SAME idempotency key + SAME request within 15 minutes — a different payer is a different payer. Every call through this relay carries a fresh key, so a retry here is always a new charge. Price with billing_quote first; verify any charge with the billing_attempts tool (own wallet: reserved vs settled, per attempt). AS OF A DATE (GR-126-5): as_of = YYYY-MM-DD or a UTC datetime (needs one entity) answers TWICE, labelled — true_at: the edges true then in VALID time (every hop: a source dates its start on/before as_of, or — start unknown — a source stated it by then, and it had not ended), with the excluded edges counted by reason (began after / ended by / first stated after / undated); and served_at: the edges GreenlandAI SERVED then in RECORD time, each with the observation it rests on (a dated archive snapshot, the record-time epoch, or a recorded version); before 2026-07-30 what we served is not recorded by id and the answer says so. One request, one price; nothing in either answer costs nothing; a bad or future as_of is a 400, not charged. WHAT YOU PAID: the JSON response carries a top-level charged_joules — the all-in PRICE of this call — and a metering block written AFTER the settle has run: {attempt_id, settlement, settled_joules, check}. metering.settlement is whether you PAID: settled · settled_zero (empty result, nothing moved) · settle_failed (delivered but UNPAID — the wallet is then locked until it clears; the next metered call 402s naming the attempt, the amount and what clears it) · released (4xx/5xx, nothing moved) · unknown. settled_joules is what actually left the wallet (0 unless settled). A cached replay carries no block.