# Finest: the right model for the job, proven before it serves you > Finest routes each request to the cheapest model proven to do that job as well as the one you asked for. Swap your API key, keep your code, pay nothing unless it saves you money. ## What Finest is Finest is a drop-in API gateway that makes sure every request is served by the cheapest model proven to do that specific job as well as the model you asked for. You change one base URL and one API key; your code keeps naming the models it already names. Most production AI spend is frontier pricing on work that never needed a frontier model — classification, extraction, tagging, routing, summarisation, reformatting. Finest finds where that is true of your traffic, proves a cheaper model holds the same quality bar, and switches only those. The jobs that genuinely need the big model keep it. Finest serves the model you asked for. It substitutes a cheaper one only where a recorded test has already proved that the cheaper model does that exact job — same prompt shape, same schema, same decoding settings, same cache mode — at a quality bar fixed before the test was run. Where no such test exists, nothing changes, and the request is served exactly as written. Every request Finest serves comes back with a receipt naming the model you asked for, the model that served you, the evidence that authorised the substitution, and both prices. You are never in the position of trusting a claim you cannot check. ## The problem: frontier strength on jobs that never needed it Almost nobody chooses a model per job. They choose one strong model at the start of a project — sensibly, because it works and because being wrong is expensive — and then never revisit it. So the model that writes the hard reasoning chain also classifies the support tickets, extracts four fields from an invoice, tags a document, reformats JSON and summarises a paragraph. Those jobs do not need frontier strength. They need to be right. And on work shaped like that, a model at a fraction of the price is frequently right just as often — not always, not on everything, but far more often than the bill suggests anyone has checked. The gap is not a rounding error. 3.4× separates the upper-quartile endpoint from the lower-quartile one across 23 verified endpoints for the same 2,000-token-in, 400-token-out task — the middle half of the catalogue, with both tails excluded, because dividing the most expensive frontier model by the cheapest small one is arithmetically true and describes a swap nobody makes. That is published list pricing, which is a fact anyone can check. Whether the cheaper endpoint actually does your job is not a fact anyone can look up, and supplying that missing half is the entire product. The same blindness runs through the rest of the bill. An output token costs about 5× what an input token costs, so an uncapped response is the most expensive thing a route can do by accident, and work nobody is waiting on can usually go to a batch tier at 50% off the standard price. ## Why competent teams do not do this themselves Not because they do not know. Because knowing is perishable. Verifying that a cheaper model holds up on one route is an afternoon of honest work: build a set of real examples, define what "as good" means before you look at the results, run both models, compare, and decide. Doing it for a dozen routes is most of a quarter. And then it expires. A new model ships next Tuesday. A provider reprices its cache writes. The same open weights behave differently on a different host. A long-context tier quietly changes where its cliff sits. Every one of those invalidates the answer you paid a quarter for, and the work to re-check it is identical to the work you just did. That is the actual shape of the problem: not a decision, a standing obligation. Nobody staffs a standing obligation to re-audit their model choices every week, which is why the choice made in the first month of a project is usually still in force in the second year, several model generations after it stopped being the right one. ## What people use instead Four things a team reaches for before this one. Each is reasonable, and each fails in a specific and predictable place. - **One strong model for everything.** The default, and the reason this product exists. Never wrong exactly — just expensive in a way that compounds quietly as traffic grows. - **A cheaper model, chosen by hand.** This works, for as long as someone has the afternoon to verify it and the discipline to re-verify every time the market moves. The failure is not the choice. It is that the choice is never revisited. - **A router that picks whatever looks capable and costs less.** Quick to adopt, and structurally unable to tell you whether quality held, because nothing measured your job before the switch. Finest is that idea with the missing half supplied. - **A gateway that charges for access.** Aggregators take a percentage of traffic to reach providers you could reach directly. That fee grows as your bill grows, which is the opposite of the incentive you want pointed at your spend. ## What you actually do: swap one key Point your OpenAI- or Anthropic-shaped client at the Finest gateway and authenticate with a Finest key. That is the integration. No SDK rewrite, no route annotations, no test corpus to assemble, no graders to write, no model ids to change. The models your application arrives with are recorded as your baseline, so nothing Finest recommends later can raise the number it measures itself against. From then on every call is served as asked until a recorded test covers that exact job on a cheaper model. - **One base URL, one key.** A signed-in human issues the key in the console. Your provider key stays where it is so that a Finest-owned refusal can fall straight back to your provider. - **Your model names do not change.** Requests keep naming the models the application already names. Substitution happens below that name, and the receipt tells you every time it did. - **One environment variable turns it off.** FINEST_DISABLE=1 sends every call straight to your provider again, with no redeploy of anything Finest owns. - **Leaving is a product, not a support ticket.** Eject provisions your own provider accounts, exports your evidence and receipts, and verifies your application no longer depends on Finest being up. ## How Finest decides a cheaper model is safe Finest publishes what it has measured itself, and today that table authorises no percentage. Until it does, no number on any Finest surface describes a saving, because the only thing worse than an unproven claim is an unproven claim with a decimal point in it. A test authorises a substitution only for the exact configuration it measured: the prompt revision, the schema, the model endpoint, the decoding parameters, the cache mode and the adapter revision. Change any one of them and the authorisation lapses until a fresh run passes. Evidence that is too broad to route on is also too broad to advertise from. Live traffic then starts on a small slice that rolls back automatically if results get worse. If a cheaper model refuses a call or returns malformed output, the call is re-run on the model you asked for, at Finest’s expense. A request that sets `x-finest-no-demote: true` is always served by the model it names. Evidence Finest ran itself is labelled Recommended, which is the weakest of the three labels and the strongest that house evidence can ever earn. Only a test on your own examples earns anything stronger. Finest will not describe its own measurement as verified for you, because it is not. ## What it costs Finest is free until it saves you money, and then costs 25% of what it saved. There is no seat price, no platform fee, no minimum, and no markup on tokens. You pay your providers what you would have paid them anyway: provider list price, passed through. Finest’s only charge is 25% of the saving it proves on a request, taken from prepaid credit at the moment it serves. Prove no savings, charge nothing. Finest bills against the lower of what you were already spending and the option it recommended, so a recommendation cannot become a more expensive baseline. And because the fee is a share of savings rather than a share of traffic, Finest earns more when you spend less — which is the only pricing shape under which the incentive to find you a cheaper model is real. - **Token cost.** Provider list price, passed through with no markup. - **Finest fee.** 25% of the saving proved on a request, debited at serve time. No allowance, no minimum. - **If nothing is saved.** Nothing is charged. There is no floor to fall back on. - **If a recommendation costs more.** It cannot raise the billing baseline. Finest measures against the lower of the two. ## What Finest will not do Each of these is a property of how the system is built rather than a policy that could be quietly revised. - **It does not keep your prompts.** No table in the codebase has a column for prompt or completion content, and Finest does not train on your traffic. Verification runs on frozen public, synthetic or CI examples; this release refuses uploaded production content outright. - **It does not pick a model from memory.** Model facts come from a registry admitted from official provider documentation, each with a current published price and a human sign-off. A vendor launch post is not a sign-off and cannot authorise a swap. - **It does not flip your traffic without a human.** Changing which model serves live traffic requires a human approver. No agent path, including Finest’s own, can approve one. - **It does not hide where it sits.** On the gateway path your requests pass through Finest’s infrastructure by explicit, disclosed choice. Several providers Finest can address process data outside the United States; the current list is at https://finest.so/sub-processors. ## What Finest is not The category is crowded with things that look similar from a distance and behave nothing alike once your traffic is inside them. - **Not a model, and not a model provider.** Finest trains nothing and hosts nothing. It routes to the models you already use, from the providers you already use. - **Not a marketplace that charges you for access.** Finest takes no margin on tokens and no fee for reaching a provider you were always going to reach. Its revenue exists only where a saving has been proven. - **Not a cheapest-model-wins router.** Price never authorises a substitution on its own. A cheaper configuration serves nothing until it has cleared a quality bar on that exact task shape, and a class that fails authorises no substitution at any price. - **Not a benchmark or a leaderboard.** A public leaderboard says a model is good in general. It cannot say whether it is good at the job you are actually sending, which is the only question that decides whether you can stop paying for the larger one. - **Not an autoscaler for quality.** Nothing degrades silently to save money. If the evidence is absent the expensive model serves the request, and the receipt says so. ## Who it is for Finest is for teams shipping production applications on the OpenAI or Anthropic APIs whose model bill has become a real line item, and whose traffic is mostly the ordinary work of software — classification, extraction, tagging, summarisation, routing, formatting — sent to a model chosen for the hardest thing the product does. It is a poor fit if your traffic is a single low-volume route, if you are pre-product and your bill is noise, or if you cannot route through third-party infrastructure at all — in which case the honest answer is not to install it. ## How to start Create a workspace at https://finest.so/sign-up, issue a key, and change the base URL your client already points at. A coding agent can do the edit: give it https://finest.so/llms.txt and it will follow the install, show you the diff and stop. Everything above is checkable before you sign up: the fee and the allowance are computed by the same code that builds a statement, the prices come from the endpoint registry the optimizer routes with, and any percentage is published from immutable verification records whose ids travel with it. https://finest.so/how-it-works has the working.