feat: a Skills checkbox in a model's Builtin Tools #31846

Problem

With a model's Builtin Tools capability on and native function calling, every active skill the user can read is listed in a system message, and the model gets the view_skill tool to load any of them on demand. This has been the case since v0.11.4.

A model's Builtin Tools section has a checkbox for each group of built-in tools, but none for skills. With all 16 checkboxes off, the model still receives the skill list and view_skill. On dev, I unticked every Builtin Tools checkbox on a model, kept the Builtin Tools capability on, and the model still called view_skill in a native function calling chat.

Today the only ways to keep skills away from one model are to turn off its Builtin Tools capability, which removes every built-in tool, switch it to legacy function calling, or to disable every toggled on skill.

Proposed behavior

Add a Skills checkbox to a model's Builtin Tools section, on by default like the others. When it is off for a model:

• the skill list is not added to the system messages for that model
• view_skill is not offered
• skills mentioned in a message, and skills attached to the model, are still added in full, as they are with built-in tools off

Use cases

• Models that should not see skills. A model built for one narrow job, such as a translator or a support assistant, gets a list of unrelated skills in every request. In my test, the model called view_skill 32 times in one reply, hitting the CHAT_RESPONSE_MAX_TOOL_CALL_ITERATIONS value I had set.
• Backends that rely on their own system prompt. In issue: Date and time answers become incorrect when a user has read access to any Skill (v0.11.4) #31535, a model behind a LangChain backend lost the date its backend supplied as soon as the user could read one skill, because the skill list arrived as a system message. A per-model switch would let an admin keep skills off that model without turning off every built-in tool.
• Keeping the other built-in tools. An admin who wants a model to keep web search, memory or knowledge tools, but not skills, has no way to do that now.

Alternatives

• Turn off the model's Builtin Tools capability. This removes every built-in tool, not only skills.
• Switch the model to legacy function calling. This changes how all tools are called, not only skills.
• Remove the user's read access to skills. This affects every model that user chats with.

Scope

One new key in the model's existing builtinTools settings, read where the skill list and view_skill are added. No change for models that do not set it.