tools.visible: selective deferred-tool visibility at startup #6368

What would you like to be added?

A new tools.visible setting in settings.json that allows users to specify which deferred tools should be visible to the LLM from the very first turn, without needing to call tool_search.

Example:

{
  "tools": {
    "visible": ["web_fetch", "monitor", "task_stop"]
  }
}

Currently, deferred tools (those with shouldDefer=true) are hidden from the initial function declaration list. The model can only discover them on-demand via tool_search. This setting would let users override that on a per-tool basis — a selected set of deferred tools would be included in the initial declaration list at session start, just like non-deferred tools.

Why is this needed?

1. Frequently-used tools should be immediately available. Tools like web_fetch, monitor, task_stop, and cron_create/list/delete are used routinely. Forcing the model to call tool_search before each first use adds latency, wastes tokens on the search round-trip, and the discovery schemas embedded in <functions> blocks.

2. Reducing tool_search calls improves KV-cache stability. Every tool_search call that reveals a deferred tool changes the prompt prefix (the deferred-tools reminder in the system prompt), which invalidates the LLM server's KV cache and forces full recomputation (~500–2000ms penalty). Making commonly-used tools visible from startup eliminates the need to discover them mid-session.

3. Existing workarounds are too coarse. Disabling ToolSearch globally (tools.toolSearch.enabled: false) makes all deferred tools visible at once, which defeats the purpose of deferred loading. Per-MCP-server alwaysLoadTools: true only works for whole MCP servers, not individual tools. There is no way to selectively promote a handful of deferred tools to visible-at-startup.

Additional context

• Related to tool_search invalidates LLM server KV-cache on every deferred-tool load #6265 — KV-cache invalidation on tool_search (this feature would reduce the number of cases where tool_search is needed)
• The existing mcpServers.<NAME>.alwaysLoadTools option (per-server) shows the pattern already exists in the system, but there is no per-tool equivalent
• The existing tools.disabled setting (in ConfigParameters, mapped from settings.tools.disabled) proves the settings.tools.* namespace is established; tools.visible would be a sibling key
• No existing issues found for this specific proposal

QwenCode QwenLLM

{
  "tools": {
    "visible": ["web_fetch", "monitor", "task_stop"]
  }
}