WebMCP & MCP API

Quick start

Browser WebMCP

Open naczarter.pl/en in a compatible browser, then check whether the registration API is available.

typeof document.modelContext?.registerTool === "function"

// Chrome 152: run in the console of this tab.
const mc = document.modelContext;
if (!mc) throw new Error("WebMCP is unavailable in this browser");
const tools = await mc.getTools();
const search = tools.find(tool => tool.name === "search_charters");
if (!search) throw new Error("NaCzarter tools are not registered in this tab");
const result = await mc.executeTool(
  search,
  JSON.stringify({ city: "Giżycko", minPeople: 6 })
);
console.log(result);

API presence alone does not prove that registration succeeded; check getTools(). This read-only example uses the JSON-string argument accepted by Chrome 152's imperative API. WebMCP is experimental; the current draft and browser releases can differ. See the Chrome API documentation.

Remote MCP

Configure https://naczarter.pl/api/mcp as a read-only Streamable HTTP endpoint. It exposes three public read tools and no reservation or payment mutation. Every POST must use Content-Type: application/json.

curl -s https://naczarter.pl/api/mcp \
  -H 'Content-Type: application/json' \
  -H 'Accept: application/json, text/event-stream' \
  -d '{
    "jsonrpc": "2.0",
    "id": 1,
    "method": "initialize",
    "params": {
      "protocolVersion": "2025-11-25",
      "capabilities": {},
      "clientInfo": { "name": "docs-example", "version": "1.0" }
    }
  }'

curl -s https://naczarter.pl/api/mcp \
  -H 'Content-Type: application/json' \
  -H 'Accept: application/json, text/event-stream' \
  -H 'MCP-Protocol-Version: 2025-11-25' \
  -d '{
    "jsonrpc": "2.0",
    "id": 2,
    "method": "tools/list"
  }'

curl -s https://naczarter.pl/api/mcp \
  -H 'Content-Type: application/json' \
  -H 'Accept: application/json, text/event-stream' \
  -H 'MCP-Protocol-Version: 2025-11-25' \
  -d '{
    "jsonrpc": "2.0",
    "id": 3,
    "method": "tools/call",
    "params": {
      "name": "search_charters",
      "arguments": {
        "city": "Giżycko",
        "minPeople": 6
      }
    }
  }'

tools/list is the runtime contract: it returns required fields, enums, limits, annotations and the exact three-tool remote catalogue. Supported protocol revisions are 2025-11-25 and 2025-06-18. The WebMCP manifest is descriptive, not runtime discovery.

Tools

This is a compact summary rendered from the shared AGENT_TOOL_CONTRACT. Use tools/list for the exact remote inputSchema, including required fields, enums and bounds.

Remote MCP exposes the first three read-only tools only. Browser WebMCP exposes all four tools. Calls to book_charter open a confirmation dialog for guests and account holders before any reservation is created.

Scroll the table horizontally to inspect every column.

Browser annotations mark discovery tools read-only and book_charter consequential. Catalogue-backed output is marked untrusted where applicable; server validation remains authoritative.

Browser vs remote

Scroll the table horizontally to compare both transports.

Browser booking

book_charter is not available over remote MCP. A compatible browser registers it for guests and signed-in users. No account required: every booking still needs explicit confirmation and human verification in the current tab.

1. 1. Quote. Call quote_charter for the selected yacht, dates and one-way option. It returns online charter price, mandatory on-site fees, currency, terms revision and a server-revalidated acceptedQuote snapshot.
2. 2. Identify. Supply the customer's name, e-mail and phone. A signed-in session with a matching verified e-mail attaches the booking to that account. Otherwise the server creates a guest reservation with a random access token; the supplied e-mail alone never authorizes account attachment in this flow.
3. 3. Confirm. NaCzarter opens its own in-tab dialog with the fresh quote, customer details, linked terms and a required consent checkbox. A human-verification proof from that dialog is bound to this booking action and checked by the server. Cancelling, expiry or timing out creates no reservation.
4. 4. Revalidate. The server validates contact details, human verification, rate and hold limits, quote snapshot, price and availability, locks the yacht row and repeats the overlap check.
5. 5. Hold. A successful call creates an unpaid PENDING order that temporarily holds the selected dates. The tool does not charge or receive payment credentials.
6. 6. Hand off. The customer opens checkoutUrl and pays personally. The result also includes statusUrl: a private guest link or the authenticated account-page URL. If checkout startup fails after the hold exists, the browser tool returns this link as bookingUrl in a handoff response. Do not create a second hold for the same dates. Guest links carry a bearer token in the URL fragment (#token=…); do not publish them or put them in analytics or tool logs.

Consent and telemetry

Browser cancellation before confirmation prevents the mutation. A late abort is not a rollback and requires state reconciliation. Booking contact data is stored on the reservation but excluded from the tool-call summary; telemetry includes a salted IP hash and user agent, so it is pseudonymous rather than anonymous. Read calls also emit operational telemetry even though they do not change booking or catalogue state.