Zed MCP: which agents use your Sume server (Panel, ACP, terminal)

In Zed, the Sume MCP entry in context_servers is used directly by Zed's own Agent, can be forwarded to external agents over ACP, and is not read by CLIs that run in a terminal thread. Those CLIs read their own MCP configuration, so a Claude Code or Codex session in a Zed terminal needs Sume added to that tool, not to Zed.

This follows Zed's Model Context Protocol page and Sume's quickstart and OAuth and API keys, read 2026-10-02.

How does Zed treat MCP in each agent path?

Zed's page has a small table. Zed Agent uses Zed-configured MCP servers directly. For External Agents, Zed can forward configured servers over ACP, and the agents may also read their native MCP config. For Terminal Threads, native CLIs and TUIs read their own configuration. The page also says Zed supports MCP's Tools and Prompts features, and that it reloads the tool list when a server sends notifications/tools/list_changed.

What does the Sume entry look like in Zed?

Zed's page shows a remote server as a url with optional headers, and says that when a remote server has no Authorization header configured, Zed prompts you to authenticate with the standard MCP OAuth flow. For Sume that gives two routes: a bare url for OAuth, or an Authorization: Bearer header carrying an API key.

{
  "context_servers": {
    "sume": {
      "url": "https://mcp.sume.com/mcp"
    }
  }
}

What changes between OAuth and a key?

With the bare url, Zed starts OAuth and Sume's consent happens on the MCP host. The default grant is mcp:read, so mutating and paid tools stay hidden unless you switch Write on at consent. With an API key in an Authorization header, Zed skips OAuth and the session sees the full hosted tool set.

Paid calls need an idempotency_key in both cases. Do not paste a key into a file you commit; Zed's user settings file is yours alone, but a shared project config is not.

Why does the tool list not refresh by itself?

Zed would pick up a list_changed notification, but Sume's server declares listChanged: false and does not send one. If you change scope from read to write, reconnect the server so Zed asks for tools/list again. Sume's server declares tools only, so the prompt side of Zed's MCP support has nothing to show for it.

To check the connection, open Settings, AI, MCP Servers and watch the indicator dot next to the server name. Zed's page says green with the tooltip "Server is active" means it is running. Then ask the agent to call mcp_health.