FoundationAgents/OpenManus · error · ValueError

Server URL is required for SSE connection

Error message

Server URL is required for SSE connection

What it means

Raised by MCPSelfCorruptAgent.initialize() when the agent's connection_type is 'sse' but the server_url argument is empty/None. The SSE transport requires an explicit http(s) endpoint to connect to, unlike stdio which launches a local command. The check is a plain falsy test, so empty strings also trigger it.

Source

Thrown at app/agent/mcp.py:61

        server_url: Optional[str] = None,
        command: Optional[str] = None,
        args: Optional[List[str]] = None,
    ) -> None:
        """Initialize the MCP connection.

        Args:
            connection_type: Type of connection to use ("stdio" or "sse")
            server_url: URL of the MCP server (for SSE connection)
            command: Command to run (for stdio connection)
            args: Arguments for the command (for stdio connection)
        """
        if connection_type:
            self.connection_type = connection_type

        # Connect to the MCP server based on connection type
        if self.connection_type == "sse":
            if not server_url:
                raise ValueError("Server URL is required for SSE connection")
            await self.mcp_clients.connect_sse(server_url=server_url)
        elif self.connection_type == "stdio":
            if not command:
                raise ValueError("Command is required for stdio connection")
            await self.mcp_clients.connect_stdio(command=command, args=args or [])
        else:
            raise ValueError(f"Unsupported connection type: {self.connection_type}")

        # Set available_tools to our MCP instance
        self.available_tools = self.mcp_clients

        # Store initial tool schemas
        await self._refresh_tools()

        # Add system message about available tools
        tool_names = list(self.mcp_clients.tool_map.keys())
        tools_info = ", ".join(tool_names)

View on GitHub (pinned to 52a13f2a57)

Solutions

1. Pass a valid server_url, e.g. await agent.initialize(connection_type="sse", server_url="http://localhost:8080/sse")
2. If loading from config, verify the mcpServers.<id>.url key exists and is non-empty before calling initialize
3. Confirm connection_type matches the transport you actually have parameters for (use "stdio" with command/args instead)

Example fix

// before
await agent.initialize(connection_type="sse")  # ValueError

// after
await agent.initialize(connection_type="sse", server_url="http://localhost:8080/sse")

def valid_sse_params(connection_type: str, server_url: str | None) -> bool:
    return connection_type == "sse" and bool(server_url and server_url.strip())

When it happens

Trigger: Calling agent.initialize(connection_type="sse") or initialize(connection_type="sse", server_url="") or omitting server_url while the agent was previously constructed with connection_type="sse". The stored self.connection_type wins whenever the passed connection_type is falsy.

Common situations: Copying a stdio MCP config and switching type to "sse" without adding a url; reading config from config.toml mcpServers where url key is missing; passing server_url=None as a default argument.

Related errors

• Command is required for stdio connection
• Unsupported connection type: {self.connection_type}
• Failed to load MCP server config: {e}
• Server URL is required.
• Server command is required.

AI-assisted analysis of FoundationAgents/OpenManus@52a13f2a57 (2026-08-15). Data as JSON: /api/errors/226a29b1d3c15ea9. Report an issue: GitHub.