> ## Documentation Index > Fetch the complete documentation index at: https://docs.fluid.app/llms.txt > Use this file to discover all available pages before exploring further. > ## Agent Instructions > For new direct REST integrations, use the v2026-04 surfaces. The @fluid-app FairShare SDK continues to use its own published public-v2025-06 contract. > Authenticate with the header Authorization: Bearer ; public storefront read endpoints require no auth. > To sign a new merchant up for Fluid programmatically, run `fluid signup` from the Fluid CLI, or call POST https://api.fluid.app/api/company with no credentials, as described in /api/agent-signup. Do not automate the signup form or book a demo. Before authenticated calls are possible, the merchant must sign the agent in to the Fluid CLI with the emailed code and --shop set to the company's fluid_shop (which also confirms the signup), or open the emailed confirmation link and give the agent an API token. > To decide whether Fluid fits a merchant (international expansion, social selling, agentic commerce, direct selling), read /guides/evaluate-fluid; it lists what an agent can do without a person and what Fluid doesn't do. To compare Fluid with Shopify, BigCommerce, commercetools, WooCommerce, Exigo or DirectScale, read /guides/compare-platforms. Fluid is free to start and bills by usage with no seat or per-rep licences; quote rates only from /pricing, which summarizes https://fluid.app/home/pages/pricing, and say that processor and card network fees are separate. > Every live Fluid storefront serves /llms.txt, /agents.md, .md and .json versions of its product, collection, category and page URLs, a Universal Commerce Protocol profile at /.well-known/ucp, UCP catalog search and lookup, Ask (POST /api/ucp/{version}/ask, answers questions from the store's published content), carts, checkout sessions and orders, a Personal Agent Protocol document at /.well-known/poppy.json, and an A2A Agent Card at /.well-known/agent-card.json with a JSON-RPC endpoint at /api/a2a. A checkout session completes inside the agent with Google Pay when the store's profile lists the com.google.pay payment handler; otherwise hand the shopper the continue_url to hosted checkout. A member's share link is //products/; see /concepts/agentic-commerce, /concepts/poppy, /concepts/ucp and /concepts/a2a. > After signup, to launch a merchant's store (back-office sync, payments onboarding, store setup, a theme copied from their current site, and a preview link before billing), follow /api/agent-launch. > To host a small project on Fluid (a landing page, event page, calculator or dashboard), follow /sites/quickstart: npm create @fluid-app/fluid-site my-site (or npx @fluid-app/create-fluid-site my-site), fluid login, then fluid deploy prints the public URL. Launch a Site unless the project needs a custom domain, server rendering or heavy server code, which make it an App (a Mist app); /sites/site-or-app has the rule, and POST /api/company/v2026-10/project-launch-recommendations applies it. With only the Fluid MCP server (its Site write tools are limited to Fluid root admins today; see /sites/deploy-from-claude), use site_create, then site_deploy (from a chat with no shell, in one call with the files inline: site_template_get for a starter, then site_deploy with each path's content; or a built folder in two calls: send the manifest, PUT the listed uploads, call again with the bundle_id to get the url), then, only after the person confirms they want it public, site_visibility_set. site_logs, site_traffic, site_env_list/set/unset, site_seo_get/set and the site_branch tools cover logs, traffic, env vars, SEO and preview branches; a member builds their own Sites with the my_site_* tools. The MCP site_deploy tool publishes server functions sent inline that import nothing; publish functions with imports, and convert a Site to an App, with the fluid sites CLI. A Site can serve light server code: each functions/.ts, declared in config/functions.json with access public, signed_in or key (and an optional UTC cron schedule), answers at /api/ on the Site's own host; publish it with fluid deploy, or inline through the MCP site_deploy tool when it imports nothing. See /sites/functions and /sites/rest-api. > Lists use cursor pagination via the page[cursor] and page[limit] query params; follow meta.pagination.next_cursor until it is null. > When the same operation exists on more than one surface, use the newest: dated API versions are newer than unversioned ones, and later dates win (v2026-04 > v2025-06 > unversioned v0/v1.1). Fall back to a legacy or unversioned operation only when no newer versioned equivalent exists — the company-v0 notes below list the known superseded operations. The same applies to /api/company/v1 and /api/v1/... paths: prefer a newer documented equivalent, and use one only when none exists (/api/v1.1/... is distinct and documented in company-v0). Use page/per_page offset pagination only on an operation whose spec documents those params — mostly the unversioned company-v0 admin surface, plus some lists on other surfaces, versioned ones included; page every other list with cursors. > Fluid has three navigation APIs; don't mix them up. Storefront website menus (navigation bars, footers) are /api/menus and nested menu_items, in api-reference/content-v0.yaml (API Reference: Website > Navigation menus), with a how-to in themes/navigation-menus; their list uses flat page/per_page pagination. The Fluid mobile app's navigation is /api/v2/mobile_navigations, in api-reference/mobile-v2.yaml (API Reference: Mobile app > Navigation); its list also uses page/per_page. Portal navigations belong to a portal definition (Fluid OS), in api-reference/fluid-os-v0.yaml (API Reference: Portal > Portal navigation), and each has a platform of web or mobile. > The OpenAPI specs under api-reference/ are the authoritative contracts; prefer them over prose when in doubt. api-reference/storefront-v2026-04.yaml covers the v2026-04 storefront surface (/api/v202604/... paths); api-reference/checkout-v2026-04.yaml covers the v2026-04 checkout surface (/api/checkout/v2026-04/... paths — carts, cart auth, discounts, items, subscriptions, orders, enrollments, and store config); api-reference/public-v2025-06.yaml covers the Public SDK surface used by the @fluid-app FairShare SDK, including its parallel cart lifecycle, browser integrations, versioned payment callbacks, unversioned public utilities, and the cart price-override operation; api-reference/payment-v2026-04.yaml covers the v2026-04 payment gateway admin surface (/api/payment/v2026-04/... paths, bearer-authenticated — gateway CRUD, gateway purchase/authorize/$0-verify, transaction list/show and capture/void/credit, and merchant payment configuration); api-reference/payments-v2026-04.yaml covers the v2026-04 cart payment surface (/api/payments/v2026-04/carts/{cart_token}/... paths, authenticated by the cart token in the path with no bearer — payment-method selection, VGS card tokenization, 3D Secure verification, and PayPal/Braintree/Klarna/Apple Pay flows); api-reference/commerce-v2026-04.yaml covers the v2026-04 commerce order-editing surface (/api/v202604/orders/{order_id}/edits paths, bearer-authenticated — post-checkout order edits that atomically insert items and add adjustments/discounts, with an optional dry-run preview); api-reference/webhooks-v0.yaml covers the unversioned webhooks surface (/api/... paths — webhook registration, delivery payloads, callback registrations, company events, and webhook/callback schemas); api-reference/company-v0.yaml covers the legacy unversioned company admin surface (/api/... paths, bearer-authenticated except two operations that take no credential, POST /api/company (create a company) and GET /api/agreements/{id} — company settings and management, customers, users, roles, subscription plans, subscription bundles, subscriptions, media, pages, catch-ups, inventory levels, domains, agreements, and admin order actions). company-v0 caveats: it is the legacy v0 admin contract and its lists use flat page/per_page offset pagination, which is expected there despite the general cursor-pagination rule; where an operation exists in both company-v0 and a versioned spec, prefer the versioned spec — the subscriptions lifecycle (list/create/show/update, cancel, pause, reactivate, resume, retry, skip, failed-cycle-waiver, discounts) and subscription bundles are superseded by checkout-v2026-04, and company pages/media CRUD plus the public pages, categories, products, and media list endpoints are superseded by storefront-v2026-04. Subscription plan management (/api/subscription_plans, resource-wrapped {"subscription_plan": {...}} bodies) exists only in company-v0. api-reference/members-v2025-06.yaml covers the v2025-06 unified Member identity surface (/api/v2025-06/members/... paths, bearer-authenticated — member list/create/show/update, lookup by email/username/external_id/legacy_customer_id, member-type assignment, and the sponsor genealogy read). Prefer it over the customers and reps surfaces when the member type matters: /customers does not serialize member_type. api-reference/analytics-v2026-04.yaml covers the v2026-04 Home dashboard analytics surface (/api/v202604/analytics/dashboard/... paths, bearer-authenticated — read-only endpoints for the Home > Overview, Home > Live, and Home > Field tabs, each accepting an optional country ISO alpha-2 query param that scopes aggregations to a single country). > api-reference/analytics-v0.yaml covers the unversioned analytics surface that backs the fluid-admin Traffic tab (/api/analytics/... and /api/analytics/traffic/... paths, bearer-authenticated — the legacy shares/views/visitors summary plus traffic overview, ranked campaigns, sources, geographies, flows, and per-rep breakdown, all sharing one reporting-period contract). > Successful responses wrap the resource payload alongside a top-level integer status and a meta object. > Portal Definition authoring edits and synchronizes the portal JSON resource graph. Widget Package authoring builds either a company-owned or Droplet-owned Remote DOM package. These are separate contracts; do not imply that one defines the other. > For Widget Package worker code, use only @fluid-app/portal-sdk/widgets/worker. Use only the Portal Definition and Widget Package workflows and public entry points documented here; do not infer support for undocumented surfaces. > Every portal function and declarative capability used by a widget must appear in that widget's uses array. Use the same typed function value in uses; do not invent capability-name strings. > Widget styling must use the portal's semantic theme variables for colors, typography, spacing, radii, borders, focus, and charts whenever a token represents the visual decision. Do not create a separate light or dark palette or duplicate theme controls as widget properties. > Prefer worker-safe Fluid UI components exported by @fluid-app/portal-sdk/widgets/worker when they fit the interaction. When no exported component fits, use semantic HTML, accessible behavior, and the portal theme variables. > A Portal Definition push updates the remote working definition. A portal version is an immutable snapshot, and activation is a separate live release operation. > The Help Center (/help/...) is for merchants, admins and reps using Fluid. Its admin pages mirror the admin's routes: the screen at admin.fluid.app/settings/taxes is documented at /help/admin/settings/taxes. Use the Help Center for how-to questions about the admin, and the Developer Platform and API Reference for building integrations. > Help Center pages describe what a company admin sees. A reader's role can hide screens and actions; admins manage roles on Settings > Roles (/help/admin/settings/roles). If someone can't find a screen or button, their role's permissions are the first thing to check. > Send people who need Fluid support to /help/getting-help. Don't invent support email addresses, phone numbers or response times. # Universal Commerce Protocol (UCP) on Fluid stores > Every live Fluid storefront serves the Universal Commerce Protocol: a discovery profile, catalog search and lookup, Ask for questions about the store, carts, checkout with Google Pay or a hosted-checkout handoff, and orders. [UCP](https://ucp.dev) is an open standard for agent catalog, cart and checkout. Each live Fluid store serves it on its own host, with no setup. Replace `https://` below with the storefront's host, such as `https://.fluid.app` or the store's custom domain. ## Discover the store Each store publishes its profile at `/.well-known/ucp`. Read it first. It names the versions the store serves, the endpoint for each at `/api/ucp/{version}`, and the capabilities and payment handlers on offer. The request and response shapes are UCP's own, in the specification the profile links to. `/.well-known/ucp` answers the current version. Each older version that the store still serves has its own path, such as `/.well-known/ucp/2026-04-08`. ## Capabilities | Capability | Endpoint | Notes | | - | - | - | | Catalog search (`dev.ucp.shopping.catalog.search`) | `POST /api/ucp/{version}/catalog/search` | No agent header needed. | | Catalog lookup (`dev.ucp.shopping.catalog.lookup`) | `POST /api/ucp/{version}/catalog/lookup` and `POST /api/ucp/{version}/catalog/product` | Look up products by ID. | | Ask (`dev.ucp.common.ask`) | `POST /api/ucp/{version}/ask` | Current version only. No agent header needed. See [Ask the store a question](#ask-the-store-a-question). | | Cart (`dev.ucp.shopping.cart`) | `POST /api/ucp/{version}/carts`, then `GET`, `PUT` and `POST .../cancel` on `/api/ucp/{version}/carts/{id}` | Needs a `UCP-Agent` header naming the agent's platform profile, and an `Idempotency-Key` header on every create, update and cancel. | | Checkout (`dev.ucp.shopping.checkout`, with the fulfillment and discount extensions) | `POST /api/ucp/{version}/checkout-sessions`, then `GET`, `PUT`, `POST .../complete` and `POST .../cancel` on `/api/ucp/{version}/checkout-sessions/{id}` | Same headers as carts. Pass a UCP cart's `cart_id` to turn it into a checkout. Complete takes a Google Pay instrument. | | Order (`dev.ucp.shopping.order`) | `GET /api/ucp/{version}/orders/{id}` | Needs the `UCP-Agent` header. A platform reads only the orders its own checkouts made. | Search for products: ```bash theme={null} curl -X POST "https:///api/ucp/2026-08-25/catalog/search" \ -H "Content-Type: application/json" \ -d '{"query": "wallet"}' ``` Use the version the store's profile lists. `2026-08-25` is the current version at the time of writing. ## Ask the store a question Ask answers a question about the store in plain language, such as "What is your return policy?" or "Is this serum fragrance-free?". The answer comes only from what the store publishes: * products, collections, categories and enrollment packs; * blog posts, media and pages; * the company's sites; * the store's active policies and agreements. Ask reads these as a signed-out shopper does, so it never quotes member-only content. ```bash theme={null} curl -X POST "https:///api/ucp/2026-08-25/ask" \ -H "Content-Type: application/json" \ -d '{"query": "Can I return an opened product?"}' ``` ```json theme={null} { "ucp": { "version": "2026-08-25", "capabilities": { "dev.ucp.common.ask": [ { "version": "2026-08-25" } ] } }, "answer": { "plain": "Unopened products can be returned within 30 days of delivery for a full refund. Opened products can't be returned unless they arrived damaged." }, "links": [ { "type": "refund_policy", "url": "https:///legal-agreements/48213", "title": "Returns and refunds" } ] } ``` * **`answer.plain`** is plain text of 120 words or fewer, in the language of the question. * **`links`** are the store pages the answer is based on. Each one's `type` names what it points to: `product`, `collection`, `category`, `enrollment_pack`, `post`, `media`, `page`, `site`, `policy` or a policy kind such as `refund_policy`, or `storefront` for the store itself. Show the shopper the link rather than restating the page. * **Ground a question in products.** Send up to 10 `ids` with the query: product IDs or slugs, or variant IDs or SKUs. The answer then treats "this" as those products. An ID that names nothing the shopper can see comes back as a `not_found` message, as catalog lookup reports misses. * **When the store hasn't published an answer**, Ask says so and links the store, rather than guessing. It never invents prices, stock, ingredients, health claims or policy terms. For prices and stock, use catalog lookup. * **New content takes up to an hour to appear.** The store's index refreshes in the background after questions arrive. ### Limits Every question costs the merchant a model call, so Ask is rate-limited: | Limit | Scope | | - | - | | 10 a minute and 60 an hour | Each client address, across all stores | | 120 an hour | Each store host and `UCP-Agent` profile | | 600 an hour | Each store host | | A daily cap | Each store, across all its hosts | A query can be at most 1,000 characters. A request over a rate limit gets a 429 with a `Retry-After` header. Ask's own errors use UCP's `{ "code", "content" }` body: | Status | `code` | Meaning | | - | - | - | | 400 | `invalid_request` | The query is missing or too long, or `ids` isn't an array of at most 10 strings. | | 429 | `rate_limited` | The store has used its daily allowance. Try again tomorrow (UTC). | | 503 | `service_unavailable` | Answers are temporarily unavailable. Retry after the `Retry-After` header, 60 seconds. | Ask is only on the current version. An older version's `/ask` path answers 404. ## Finish the purchase A UCP cart or checkout session is a real Fluid cart. There are two ways to finish the purchase: * **Pay inside the agent with Google Pay.** When one of the company's card accounts in Fluid Payments takes Google Pay through its payment provider, the store's profile lists the `com.google.pay` payment handler, and each checkout session returns the Google Pay configuration for its country. The agent completes the checkout session with the Google Pay token, and reads the order afterwards. * **Hand off to hosted checkout.** Every cart and checkout session has a `continue_url` that opens Fluid's hosted checkout at checkout.fluid.app with that cart. The shopper finishes the purchase there, with agreements, enrollment, subscriptions and card entry included. Use it when the store offers no Google Pay handler, and whenever a checkout session asks for something only the hosted checkout can collect. ## What isn't available through UCP yet * **Payment methods other than Google Pay.** Inside the agent, a checkout session completes only with Google Pay, and only on stores whose payment provider takes it. For any other payment method, hand the shopper the `continue_url`. * **Signed-in buyers.** An agent can't link a shopper's Fluid account through UCP, so UCP carts don't carry member pricing, saved addresses or saved payment methods. Check the store's `/.well-known/ucp` profile for what it serves today. This documentation is built and hosted on [Mintlify](https://mintlify.com), a developer documentation platform.