https://www.v0.build/docs/api/mcp?webmcp-script

1(() => {
2  "use strict";
3  const config = {"endpoint":"https://www.v0.build/docs/api/mcp","tools":["search_docs"],"credentials":"same-origin"};
4  const provider = [
5    typeof document !== "undefined" && document.modelContext,
6    typeof navigator !== "undefined" && navigator.modelContext,
7  ].find((candidate) => candidate && typeof candidate.registerTool === "function");
8  if (!provider || typeof provider.registerTool !== "function") {
9    return;
10  }
11
12  let protocolVersion = null;
13  let requestId = 0;
14
15  async function rpc(method, params, isNotification, signal) {
16    const body = { jsonrpc: "2.0", method };
17    if (params !== undefined) body.params = params;
18    if (!isNotification) body.id = ++requestId;
19    const headers = {
20      "content-type": "application/json",
21      accept: "application/json, text/event-stream",
22    };
23    if (protocolVersion) headers["mcp-protocol-version"] = protocolVersion;
24    const res = await fetch(config.endpoint, {
25      method: "POST",
26      credentials: config.credentials,
27      headers,
28      body: JSON.stringify(body),
29      signal,
30    });
31    if (isNotification) return null;
32    if (!res.ok) {
33      throw new Error("MCP request failed: HTTP " + res.status);
34    }
35    const contentType = res.headers.get("content-type") || "";
36    if (contentType.includes("text/event-stream")) {
37      return parseSse(await res.text(), body.id);
38    }
39    return unwrap(await res.json(), body.id);
40  }
41
42  function parseSse(text, id) {
43    for (const event of text.split(/\r?\n\r?\n/)) {
44      const data = event
45        .split(/\r?\n/)
46        .filter((line) => line.startsWith("data:"))
47        .map((line) => line.slice(5).replace(/^ /, ""))
48        .join("\n");
49      if (!data) continue;
50      let message;
51      try {
52        message = JSON.parse(data);
53      } catch {
54        continue;
55      }
56      if (
57        message &&
58        message.id === id &&
59        ("result" in message || "error" in message)
60      ) {
61        return unwrap(message, id);
62      }
63    }
64    throw new Error("No MCP response found in event stream");
65  }
66
67  function unwrap(message, id) {
68    if (message && message.error) {
69      throw new Error(
70        message.error.message || "MCP error " + message.error.code,
71      );
72    }
73    if (!message || message.id !== id) {
74      throw new Error("Unexpected MCP response");
75    }
76    return message.result;
77  }
78
79  (async () => {
80    const init = await rpc("initialize", {
81      protocolVersion: "2025-06-18",
82      capabilities: {},
83      clientInfo: { name: "mcp-handler/webmcp", version: "1.0.0" },
84    });
85    protocolVersion = (init && init.protocolVersion) || "2025-06-18";
86    await rpc("notifications/initialized", undefined, true).catch(() => null);
87
88    let cursor;
89    do {
90      const listed = await rpc("tools/list", cursor ? { cursor } : {});
91      for (const tool of (listed && listed.tools) || []) {
92        if (!config.tools.includes(tool.name)) continue;
93        try {
94          await provider.registerTool({
95            name: tool.name,
96            title: tool.title || tool.annotations?.title || tool.name,
97            description: tool.description || tool.title || tool.annotations?.title || tool.name,
98            inputSchema: tool.inputSchema,
99            annotations: { readOnlyHint: tool.annotations?.readOnlyHint === true },
100            execute: (args, options) =>
101              rpc("tools/call", { name: tool.name, arguments: args || {} }, false, options?.signal),
102          });
103        } catch (error) {
104          console.warn("[mcp-handler/webmcp] failed to register tool " + tool.name + ":", error);
105        }
106      }
107      cursor = listed && listed.nextCursor;
108    } while (cursor);
109  })().catch((error) => {
110    console.warn("[mcp-handler/webmcp] failed to register tools:", error);
111  });
112})();