langflow-ai/langflow · error · Error

No valid MCP server found in the input.

Error message

No valid MCP server found in the input.

What it means

Thrown by extractMcpServersFromJson when the input parsed successfully as JSON but none of the recognized shapes matched: no mcpServers object, no top-level array of server configs, and no single object with command/url keys. serverEntries stays empty, so there is nothing that even looks like an MCP server definition.

Source

Thrown at src/frontend/src/utils/mcpUtils.ts:74

    Object.values(parsed).some(
      (v) => v && typeof v === "object" && ("command" in v || "url" in v),
    )
  ) {
    serverEntries = Object.entries(parsed).filter(
      ([, v]) => v && typeof v === "object" && ("command" in v || "url" in v),
    );
  }
  // Case 3: single server object
  else if (
    parsed &&
    typeof parsed === "object" &&
    ("command" in parsed || "url" in parsed)
  ) {
    serverEntries = [["server", parsed]];
  }

  if (serverEntries.length === 0) {
    throw new Error("No valid MCP server found in the input.");
  }
  // Validate and map all servers
  const validServers = serverEntries.filter(
    ([, server]) => server.command || server.url,
  );
  if (validServers.length === 0) {
    throw new Error("No valid MCP server found in the input.");
  }
  return validServers.map(([name, server]) => ({
    name: name.slice(0, 30),
    command: server.command,
    args: server.args || [],
    env: server.env && typeof server.env === "object" ? server.env : {},
    url: server.url,
    headers:
      server.headers && typeof server.headers === "object"
        ? server.headers
        : {},

View on GitHub (pinned to 976ec789d2)

Solutions

1. Restructure the JSON to one of the three accepted shapes: {mcpServers:{name:{command|url,...}}}, an array of {command|url} objects, or a single {command|url} object
2. Check the key is exactly 'mcpServers' (case-sensitive) and its value is a non-empty object
3. If migrating from another client format, map its server key into mcpServers before importing

Example fix

// before
{"servers": {"fs": {"command": "npx"}}}

// after
{"mcpServers": {"fs": {"command": "npx"}}}

const parsed = JSON.parse(text);
const hasServerShape =
  (parsed?.mcpServers && typeof parsed.mcpServers === "object") ||
  Array.isArray(parsed) ||
  (typeof parsed === "object" && ("command" in parsed || "url" in parsed));
if (!hasServerShape) showFormatHint();

function looksLikeMcpConfig(v: unknown): boolean {
  if (typeof v !== "object" || v === null) return false;
  const o = v as Record<string, unknown>;
  if (o.mcpServers && typeof o.mcpServers === "object" && Object.keys(o.mcpServers).length > 0) return true;
  if (Array.isArray(v) && v.length > 0) return true;
  return "command" in o || "url" in o;
}

try { extractMcpServersFromJson(input); }
catch (e) {
  if (e instanceof Error && e.message.startsWith("No valid MCP server")) {
    showAcceptedFormatsHelp();
  } else throw e;
}

When it happens

Trigger: Passing valid JSON that is a different payload entirely — e.g. an API response, a config with servers nested under a custom key like 'servers' or 'tools', or {mcpServers: {}} with an empty object (falsy, fails the mcpServers check).

Common situations: Wrong nesting level (servers under mcpServers.servers), renamed top-level key from a different MCP client's config format, or empty-object configs after sanitization.

Related errors

• Invalid JSON format.
• Invalid flow data
• Failed to install MCP
• Deployment name is required
• error: invalid JSON in {source}: {exc}

AI-assisted analysis of langflow-ai/langflow@976ec789d2 (2026-08-14). Data as JSON: /api/errors/aa64bbd978eda022. Report an issue: GitHub.