BerriAI/litellm · error · ValueError

MCP server '{server.server_id}' missing required OAuth2 fiel

Error message

MCP server '{server.server_id}' missing required OAuth2 fields: client_id={bool(server.client_id)}, client_secret={bool(server.client_secret)}, token_url={bool(server.token_url)}

What it means

Error "MCP server '{server.server_id}' missing required OAuth2 fields: client_id={bool(server.client_id)}, client_secret={bool(server.client_secret)}, token_url={bool(server.token_url)}" thrown in BerriAI/litellm.

Source

Thrown at litellm/proxy/_experimental/mcp_server/oauth2_token_cache.py:123

        async with self._get_lock(identity):
            cached = self.get_cache(identity)
            if cached is not None:
                return cached

            token, ttl = await self._fetch_token(server)
            self.set_cache(identity, token, ttl=ttl)
            return token

    async def _fetch_token(self, server: "MCPServer") -> tuple[str, int]:
        """POST to ``token_url`` with ``grant_type=client_credentials``.

        Returns ``(access_token, ttl_seconds)`` where ttl accounts for the
        expiry buffer so the cache entry expires before the real token does.
        """
        client: Final = get_async_httpx_client(llm_provider=httpxSpecialProvider.MCP)

        if not server.client_id or not server.client_secret or not server.token_url:
            raise ValueError(
                f"MCP server '{server.server_id}' missing required OAuth2 fields: "
                f"client_id={bool(server.client_id)}, "
                f"client_secret={bool(server.client_secret)}, "
                f"token_url={bool(server.token_url)}"
            )

        token_request: Final = build_upstream_oauth2_token_request(
            server,
            auth_method=server.token_endpoint_auth_method,
            client_id=server.client_id,
            client_secret=server.client_secret,
        )
        data: Final[dict[str, str]] = {
            "grant_type": "client_credentials",
            **token_request.body,
        }
        if server.scopes:
            data["scope"] = " ".join(server.scopes)

View on GitHub (pinned to 77b7c6c40c)

Solutions

1. Set client_id, client_secret, and token_url on the MCP server config.

Example fix

Configure all three OAuth2 fields for the server.

When it happens

Trigger: Thrown at litellm/proxy/_experimental/mcp_server/oauth2_token_cache.py:123 when the library encounters an invalid state.

Common situations: See trigger scenarios.

AI-assisted analysis of BerriAI/litellm@77b7c6c40c (2026-08-18). Data as JSON: /api/errors/52053b3d186dba15. Report an issue: GitHub.