Claude mcp_tool_listing pin: what a Sume tool list depends on

With the mcp-client-2026-09-15 beta header, a Claude API response records each server's fetched tool list in an mcp_tool_listing block, and sending it back pins that list. For Sume the pinned list is only as good as the scope of the session that fetched it: an OAuth mcp:read session sees read-only tools, and Sume does not push tool-list change notifications.

The Claude behavior is from the release notes read 2026-10-01; the Sume behavior from MCP tools and gates and the server source.

What does the release note say?

The September 22, 2026 entry says tools can be defined inside a mid-conversation system message with the inline-tools-2026-09-15 beta header. With the MCP connector's mcp-client-2026-09-15 header as well, the definition can be an MCP toolset, and "a response records each server's fetched tool list in an mcp_tool_listing block, which pins that list when you send it back." The excerpt does not say how long a pin lasts, so read the migration guide before relying on it.

What decides which tools Sume lists?

Visibility follows the credential. Mutating and paid tools are hidden until the session has mcp:write or an API key. Default hosted OAuth grants read-only access (mcp:read).

Will a pinned list notice a scope change?

Do not assume so. The server's initialize response sets tools: { listChanged: false }, so it does not tell a client its list changed. If a user later grants Write, or you switch from OAuth to an API key, a list pinned earlier still shows the read-only set. Fetch a new listing in the new session and pin that one. See tools/list freshness for the per-session visibility details.

What should I do about it?

Pin only after the credential is final for that conversation. Ask the agent to call tools_list once after connecting, as the quickstart suggests, and use tools_schema for the contract of a single tool rather than trusting a cached description. If a tool you expect is missing, check the scope first: an insufficient_scope error or a missing paid tool usually means a read-only session. The connector itself is covered in Claude API MCP connector.