MCP Apps
ui_resource and ui_tool_input_partial SSE events; sandbox origin wiring.
GitHub issue pickers need the context toolset
Section titled “GitHub issue pickers need the context toolset”GitHub’s MCP App for issue_write fills its label, assignee and milestone
pickers by calling ui_get, an app-only tool (hidden from the model, callable
by the App). ui_get lives in GitHub’s context toolset, and the
per-toolset URLs (https://api.githubcopilot.com/mcp/x/issues) serve only the
toolset they name. On those URLs the App’s call fails with
unknown tool "ui_get", and /mcp/x/issues,context lists no tools at all.
Configure the connector on the base URL and choose the toolsets with a header:
| Field | Value |
|---|---|
| Server URL | https://api.githubcopilot.com/mcp/ |
| Custom header | X-MCP-Toolsets: issues,context |
Keep the Available Tools list to the tools the model should see.
App-only tools such as ui_get pass that list automatically, so the model’s
view does not change. Without the header the base URL serves GitHub’s whole
default toolset, so the header keeps what the server exposes to what you use.
See Tools.