MCP running-tool label lowercases internal capitalization (`ListSomething` → `Listsomething`)

Open 💬 1 comment Opened Apr 14, 2026 by cassxw

What version of the IDE extension are you using?

openai.chatgpt@26.409.20454

What subscription do you have?

Business

Which IDE are you using?

VS Code

What platform is your computer?

Microsoft Windows NT 10.0.26200.0 x64

What issue are you seeing?

In Codex VS Code, the in-progress running-tool label for MCP tools lowercases internal casing.

Example:

  • Intended tool display: ListSomething
  • Running label shown: Listsomething

This is a UI-label issue; tool invocation itself succeeds/fails independently as normal.

What steps can reproduce the bug?

  1. Register an MCP tool with internal capitalization and explicit display metadata:

``json
{
"name": "mcp__serverName__ListSomething",
"title": "ListSomething",
"annotations": { "title": "ListSomething" },
"inputSchema": {
"type": "object",
"properties": {
"query": { "type": "string" }
},
"required": ["query"]
}
}
``

  1. In Codex VS Code, ask the agent to invoke the tool:

``
mcp__serverName__ListSomething({ "query": "test" })
``

  1. While the call is running, observe the spinner/status label in the transcript. Observed label: Listsomething.

What is the expected behavior?

The running-tool label should preserve capitalization and show ListSomething, ideally using MCP display metadata (title or annotations.title) when present.

Additional information

Server-side MCP metadata for this tool is already emitted as:

  • name: mcp__serverName__ListSomething
  • title: ListSomething
  • annotations.title: ListSomething

Invocation identifier is exact-case and callable as mcp__serverName__ListSomething.
This appears limited to MCP tool label rendering in Codex VS Code.

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