Gemini CLI 63-character tool names: Sume's longest is 45

Gemini CLI will not cut any of Sume's hosted MCP tool names, because the longest one becomes 45 characters after the prefix and the limit is 63. You can name the server up to 22 characters before the longest Sume tool would be truncated.

The Gemini CLI MCP page (read 2026-10-10) says tools are namespaced as mcp_{serverName}_{toolName}, that characters other than letters, numbers, underscore, hyphen, dot and colon are replaced with underscores, and that names longer than 63 characters are truncated. I checked that against the tool names in Sume's tools and gates page.

The arithmetic

With a server named sume, the prefix mcp_sume_ is 9 characters. The longest listed tool is avatar-video-previews_generate_video at 36 characters, which makes 45. The 63-character limit leaves 18 characters of headroom. Put differently, the server name could be 22 characters long, since 63 minus mcp_ (4), minus the closing underscore (1), minus 36 is 22.

Hyphens are allowed by the sanitizing rule, so names such as avatar-image-to-video_create pass through unchanged and are not rewritten with underscores.

Where the limit would bite

A long server alias is the usual cause. If you name the server something like sume-production-video-workspace, that is 32 characters, and the longest tool would become 4 + 32 + 1 + 36 = 73 characters, over the limit. Two long tools whose first 63 characters match would then collide after truncation. Keep the alias short and stable.

A second place is a second server that exposes similar tool names. The prefix keeps them apart as long as the server names differ, but a collision on truncated names is still possible for long aliases, so list the tools after you add a server and compare the names.

• Use a short alias such as sume.
• Use letters, numbers, underscores and hyphens only.
• Keep the alias free of spaces, which the sanitizing rule would replace.

Timeouts, trust and includeTools

The same page gives a default timeout of 600,000 ms (10 minutes) and a trust flag that bypasses confirmation dialogs. Sume's remote jobs_wait still ends each call within 55 seconds, so the 10 minute default is not the limit that matters. Treat wait_slice_expired as a signal to wait again with the same ids.

Do not set trust: true on a server that has paid tools. Use includeTools as an allowlist or excludeTools, which takes precedence, to keep paid tools out. Sume's tool gates still require an idempotency_key and the wallet check, but a confirmation dialog is the only human decision in the loop.

A config you can paste

A minimal entry in settings.json uses httpUrl and a header that reads the key from your shell. Confirm that your installed Gemini CLI expands $SUME_API_KEY in header values, since this post did not verify that; run gemini mcp list after saving, because a server that shows as disconnected usually has an empty variable rather than a wrong URL.

Keep the key out of the file. Sume accepts an API key as Authorization: Bearer or x-api-key on the MCP endpoint, so either header form works. If you would rather not handle a key at all, the OAuth route in the Sume docs gives a read-only grant by default, and Write is opt-in on the consent page.

{
  "mcpServers": {
    "sume": {
      "httpUrl": "https://mcp.sume.com/mcp",
      "headers": { "Authorization": "Bearer $SUME_API_KEY" },
      "includeTools": ["tools_list", "mcp_health", "account_me", "balance_get", "jobs_wait"]
    }
  }
}

How to verify

Add the server and list tools. gemini mcp add writes to settings.json, and gemini mcp list shows servers with connection status. Then ask the agent to call tools_list and compare its names with what Gemini shows. For the remote URL, use httpUrl for streamable HTTP, because url is the SSE form in Gemini's docs; Sume's endpoint is the streamable HTTP one at https://mcp.sume.com/mcp.