Add `title` property to `ModelContextTool `

[DavidMulder0]

This spec says name "is used by agents to reference the tool when making tool calls.". In the current MCP spec name is "intended for programmatic or logical use, but used as a display name in past specs". The problem is that name is something you use in code (e.g. in a 'toolactivated' event handler), but at the same time it should be shown to the user. The way the MCP spec nowadays handles this is that they added a second property called title:

name: string

Intended for programmatic or logical use, but used as a display name in past specs or fallback (if title isn’t present).

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title?: string

Intended for UI and end-user contexts — optimized to be human-readable and easily understood, even by those unfamiliar with domain-specific terminology.

If not provided, the name should be used for display (except for Tool, where annotations.title should be given precedence over using name, if present).

Source: https://modelcontextprotocol.io/specification/2025-11-25/schema

And to quote the MCP spec a bit more to justify the general need to show tool names to users

For trust & safety and security, there SHOULD always be a human in the loop with the ability to deny tool invocations.

Applications SHOULD:

• Provide UI that makes clear which tools are being exposed to the AI model
• Insert clear visual indicators when tools are invoked
• Present confirmation prompts to the user for operations, to ensure a human is in the loop

Source: https://modelcontextprotocol.io/specification/2025-11-25/server/tools

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Also: Are diacritics and spaces allowed in name? I vaguely recall that many MCP clients don't allow that, but neither the MCP spec nor the WebMCP spec seems to put any limit on it.

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Lastly: The above was a real hurdle I hit when trying to link up some code to WebMCP: Description should probably be localized based on the locale of the page, but then you either localize name as well (gets weird in code) or you don't and you have english mixed into the text shown to the user.

[kenchris]

We probably need to state that title doesn't have to be included in the definition shared with the LLM itself. Another option would be to have it be part of annotations: or similar. I expect that we might want to expand this to include icons to show in UI, just like Gemini shows the Spotify logo when interacting with Spotify. (Potentially, favicons can cover most of these use-cases, unless we want different icons per tool etc)

[My own prototype implementation of WebMCP actually adds both title and icon support, so I myself needed this]

[DavidMulder0]

title seem from my POV to be a required property (as tools need to be shown to the user, and those need to be localized). icons are a nice to have IMHO. Personally for something that should always be filled out for all tools it feels 'wrong' to 'hide' it in the 'annotations'.

[domfarolino]

title seem from my POV to be a required property

I agree title is more important than icon, but neither are required per the MCP spec, right?

[DavidMulder0]

title was only added to the 2025-06-18 version of the MCP specification, so title in MCP had to be optional to be backwards compatible with previous versions. For WebMCP there is no such limitation, so title can be required from v1. Note how the quote in the opening post describes name as "used as a display name in past specs". Without title you either have no display name (obviously bad for a HITL flow) or you require webpages to localize the tool name which is bound to cause issues (unsupported characters ending up in tool names is the one I walked up against, etc.)

Timeline:

• Original version had name, description, and inputSchema
• 2025-03 version added annotations
• 2026-06 version added outputSchema and title
• 2026-11 version added execution