What probably matters to youSection of the release
What
Plugins and mods can add their own tools with $.tool.register. It now accepts an isDeferred option. A deferred tool is not described to the model up front. It loads only when it is found through tool search.
The accepted shape is now { name, description, inputSchema?, isDeferred? }. name is letters, digits, _ or -, up to 64 characters.
isDeferred must be a true or false value. Anything else is rejected with an error that says so.
The MCP tools/list response now adds extra fields to each tool from a helper.
Why
Plugin authors can keep rarely used tools out of the prompt, so they take no room until they are needed.
One source agreesOne thing we can check says the same as this entry.
Anthropic's release notes agreeAdded isDeferred to $.tool.register for mods: false lists the tool's schema in the prompt from the start instead of behind tool search
