# Retrieve experiment cost model `GET /api/v1/experiment-cost-model` The merchant's real contracted payment-processing and carrier rates, which is PER-ORDER MARGIN and the most commercially sensitive figure this API serves. It is why read_experiments is a grant of its own rather than part of read_products: a key granted the catalogue has not been granted the markup on it. Read-only, permanently. Rewriting a rate silently restates every profit figure in every result snapshot the merchant reads back, with nothing erroring anywhere, so no write_experiments scope exists to be minted. payment_fee_fixed_minor is MINOR UNITS AND THE TABLE CARRIES NO CURRENCY COLUMN: the platform applies the same flat figure to an order in any currency, so the store's default currency is the only defensible reading. A store that has never written a cost model answers 200 with every rate at 0 and updated_at null, which is the platform's own fail-safe: profit is then exactly the pre-cost figure rather than a wrong cost subtracted. ## Responses - `200` — Success - `400` — The request was refused before any state changed. `code` is one of: `invalid_body`, a write body this route will not take. `reason` partitions it and `field` names the key when one key is at fault. `invalid_query`, a query parameter, including limit and after. `invalid_text`, a NUL byte or bytes that are not valid UTF-8 anywhere in the path, the query or the body. Strip control characters before sending. `idempotency_key_required`, a write sent without the Idempotency-Key header. `invalid_request`, an Idempotency-Key longer than 255 bytes. Routes add their own codes for rules only they know. Switch with a default arm. - `401` — No credential, or one this API does not accept. `code` is always `unauthorized`. THE BODY IS DELIBERATELY UNINFORMATIVE. An expired key, a revoked key, a publishable key, a key belonging to another merchant and a key that never existed are all refused with the same bytes, so this response cannot be used to probe which keys exist. Check the key's state in the dashboard rather than inferring it here. Send the key as `Authorization: Bearer ` or as `X-API-Key: `. It is never accepted in a query string. - `403` — The key lacks the read_experiments scope. `code` is `insufficient_scope` and the message names the scope to ask the merchant for. - `429` — Too many requests. `code` is `rate_limited`. Two limits apply independently: one on the credential and the route family, one on the client address. The headers describe whichever has less left, so honouring Retry-After always clears the window that bound. - `default` — Any status this operation does not list, in the same envelope. A 5xx means the request may or may not have applied. Retry it with the SAME Idempotency-Key: that is the only way to find out without risking a duplicate, and it is what the key is for. A few 4xx conditions arrive here rather than as a listed status because they depend on the merchant's plan or on a module being wired: 402 when a quota or a plan limit is reached, and 503 when a capability the route needs is not configured on this deployment. Both carry a `code` naming which. ## Example ```bash curl --request GET \ --url 'https://api.mercemur.com/api/v1/experiment-cost-model' \ --header 'Authorization: Bearer ' ```