I haven't seen the 405 mentioned in the docs, so take this as an educated guess. As far as I can tell from the get-started page, the OS11 MCP server runs locally inside Service Studio (Edit > MCP Server) and exposes an endpoint like http://127.0.0.1:PORT/mcp, which you register in your MCP host's configuration rather than open in a browser. A plain browser request is a GET, and an MCP endpoint normally only answers the protocol's own requests, so a 405 when browsing it is probably expected. A better test is to add the URL to your MCP host and approve the connection dialog that Service Studio shows. If the host also fails to connect, double-check that the port matches the one shown in the MCP Server window and that the server is started.

@Rishabh Tailor :  Please follow the steps to make it work. Execute the following from Powersell ( assuming you are on Windows )

1. Install Claude Code (Powershell - > irm https://claude.ai/install.ps1 | iex )
2. Login to Claude from console ( Powershell -> claude -> it will generate a url for you to login and once done you need to paste back a token )
3. claude mcp add --transport http servicestudio http://127.0.0.1:41820/mcp
4.  Install the skill by a) git clone https://github.com/OutSystems/outsystems11-mcp.git b) cd outsystems11-mcp c) powershell -ExecutionPolicy Bypass -File scripts\install.ps1
5. Now authorise from Service Studio
6. Finally verify ie as questions from claude console eg: Summarize the module open in Service Studio.

btw you can see the steps @ https://github.com/OutSystems/outsystems11-mcp

This works in Claude Desktop also. Use its terminal to connect the mcp and from the settings upload the skills.