# Connect citature to your agent. citature is an MCP server. Register it once and your agent gets every tool below, each returning its whole answer — a receipt, or an estimate for a survey — as `structuredContent`, so a claim in a model's answer can be checked against the record it came from without trusting citature. - Endpoint — https://mcp.citature.com/mcp - Transport — streamable HTTP, stateless - Free without a credential — 7 tools - Metered, bearer token required — 4 tools ## The endpoint Stateless — every request is independent, so there is no session to keep open and no handshake to resume. Any MCP client connects with the same block\*: > \* Clients differ on the key naming the transport. If yours rejects this block, check its own documentation for the spelling it expects; the URL is the part that matters. ``` { "mcpServers": { "citature": { "type": "http", "url": "https://mcp.citature.com/mcp" } } } ``` ## Authorization The free tools answer without one. Register the server, list the tools, and look up a food, a supplement label, a drug label, a substance or a reference amount — real receipts, cited to the record, before anything is agreed. The priced tools require a bearer token†, and so does a tool name the catalogue does not carry. > † A token must be issued for this resource; one minted for a different resource is refused even when it is otherwise valid. A token that is presented is always checked, on a free tool as much as a priced one — an expired credential is told so rather than quietly served the free tier. OAuth 2.1, with citature as the resource server. A client holding no token discovers where to get one from the protected-resource metadata, served without credentials: ``` https://mcp.citature.com/.well-known/oauth-protected-resource/mcp ``` Every step of obtaining one is a request an agent can make on its own, up to the single point a person signs in and approves the client: [the credential walkthrough](https://citature.com/auth.md) gives them in order — discovery, registering a client, the exchange, what each refusal code means, and how long a token lasts. That person signs in to a citature account, and it is the account rather than the client that the approval is recorded against and that priced answers are billed to. The account's first priced answer starts its billing, with no card taken in advance: at the end of each monthly billing period an invoice for that period's priced answers is emailed to the account's address, to be paid on the hosted invoice page it links to. The [terms](https://citature.com/terms/) set out what is billed and what never is, and [refunds](https://citature.com/refunds/) how a charge made in error is corrected. A client registers without an account and gets as far as the consent screen. [Sign in](https://auth.citature.com/login), or [ask to be told when accounts open](https://auth.citature.com/signup). Status. New accounts are not open yet: the sign-up page takes an address and writes to it when they are. Account billing runs in test mode: a priced answer is metered, and no money is taken for it. A payment made with a call settles on the Tempo test network, in test funds that carry no value. ## Paying per call, without an account Each tool is also an HTTP operation on the same host, `POST /v1/tools/`, taking the tool's arguments as its JSON body and answering with the same receipt or estimate. A priced one can be paid for with the request, by an agent holding no account. The operations open to per-call payment, and the offer each is paid by, are listed in this document; an operation it lists without an `x-payment-info` offer is not open to it‡: > ‡ An open operation answers a call carrying no payment with 402 and a challenge, under the HTTP `Payment` authentication scheme: the offer's price and stablecoin, the Tempo chain it is paid on, and the address it is paid to. The challenge is what a payment is made against, whatever a cached copy of the document said. ``` https://mcp.citature.com/openapi.json ``` Paid this way, a metered tool costs the second price its row among the tools carries, under what an account is billed. No payment made with a call is taken for less than $0.50, the least the payment processor records one for, so a call paid this way costs what an account is billed for it or $0.50, whichever is more. The payment is sent only once the answer is in hand. An answer that found nothing is served free and sends nothing; a payment the network refuses withholds the answer, and citature takes nothing. A paid answer carries a `Payment-Receipt` header naming the transaction. The [terms](https://citature.com/terms/) and [refunds](https://citature.com/refunds/) cover a per-call payment as they cover a billed call. ## The tools Of the 11, 7 restate a public record and cost nothing. The other 4 do the work nobody else assembles — one substance vocabulary across food, supplement and regulatory records — and those are metered per served answer. ### Free · 7 - [gtin_resolve](https://citature.com/tools/gtin_resolve/) - [food_lookup](https://citature.com/tools/food_lookup/) - [supplement_lookup](https://citature.com/tools/supplement_lookup/) - [drug_label_lookup](https://citature.com/tools/drug_label_lookup/) - [ingredient_resolve](https://citature.com/tools/ingredient_resolve/) - [substance_lookup](https://citature.com/tools/substance_lookup/) - [reference_amounts](https://citature.com/tools/reference_amounts/) ### Metered · 4 - [rule_evaluate $0.05 / evaluation $0.50 paid with the call](https://citature.com/tools/rule_evaluate/) - [enforcement_check $0.05 / check $0.50 paid with the call](https://citature.com/tools/enforcement_check/) - [adverse_events $0.05 / check $0.50 paid with the call](https://citature.com/tools/adverse_events/) - [dietary_intake $0.05 / estimate $0.50 paid with the call](https://citature.com/tools/dietary_intake/) > How a call is billed > > A call bills at the rate of the tool it invokes. A free tool never reaches the meter at all — not a charge of zero, no metering call on its path — and a metered tool is charged only once its answer is in hand, so a call that returned nothing is never billed. Each metered row carries what an account is billed, and under it what a call paid for with the call costs. [What each one answers →](https://citature.com/tools/) ## What a call returns An answer over a record comes back as a receipt; an answer over a survey sample comes back as an estimate, the receipt's sibling, carrying the survey design in place of a record identity. [A receipt, field by field →](https://citature.com/receipts/) [The estimate envelope →](https://citature.com/receipts/#estimate) ## What it cites - USDA FoodData Central fdc - NIH ODS Dietary Supplement Label Database dsld - openFDA openfda - National Health and Nutrition Examination Survey (NHANES) nhanes - FDA Substance Registration System (UNII) unii - Electronic Code of Federal Regulations ecfr ## Guardrails These ship in the `guardrails` field of every answer and in the instructions the server hands over when an agent connects, which every tool description points to, so an agent reads them before it spends anything. - **Not advice**: Research over public records and product labels — not medical, nutritional, or safety advice. - **No verdicts**: citature reports what the record says. It never renders a verdict, a pass/fail, a diagnosis, or a recommendation, and is not a substitute for a clinician. - **No individuals**: Answers are product-, substance- or population-level only — foods, supplements, labels, substances, enforcement actions, and dietary intake as a weighted survey estimate. No answer returns or describes an individual person, and citature links no record to individually identifiable data. - **Silence is not absence**: A record that does not declare something is not a record declaring its absence. citature reports what a record states; it cannot report what a product does not contain, or what a population did not consume. - **A Daily Value is not a DRI**: A Daily Value is a labelling reference from federal regulation, not a Dietary Reference Intake. citature carries no licensed source for Dietary Reference Intakes and does not estimate whether anyone meets a nutrient requirement. - [Wiring it up →](https://citature.com/help/) - [Questions →](https://citature.com/faq/) - [Receipts →](https://citature.com/receipts/) --- The page this is the markdown of: