[Bug]: MCP clients do not get the parameter descriptions written for T3 tools #35015

Before submitting

• I searched existing issues and did not find a duplicate.
• I included enough detail to reproduce or investigate the problem.

Area

apps/server

Steps to reproduce

1. Start T3 Code from main with vp run dev and create a pairing code with t3 auth pairing create.
2. Connect an MCP client to the server's /mcp endpoint, sign in, and approve it with the pairing code (Read only is enough).
3. Call tools/list and look at the title and clientRequestId parameters of t3_thread_update, and the clientRequestId parameter of delegate_task or t3_thread_send.

Expected behavior

Each parameter carries the description written for it in the tool's schema, so the agent knows what to pass. For t3_thread_update, title should say "New concise display title. Required only when action is rename." and clientRequestId should say "Stable idempotency key to reuse when retrying this mutation." For delegate_task and t3_thread_send, clientRequestId should say "Reuse it to retry the same call. A new call gets a new key."

Actual behavior

Those parameters arrive as a bare {"type":"string"} with no description. None of the three texts appears anywhere in the tools/list reply. Other parameters keep theirs: delegate_task > mode has its description. So an agent is not told that title is only for a rename, or how to use the retry key.

Impact

Minor bug or occasional failure

Version or commit

main, commit b68aedf

Environment

macOS 27.0.1, T3 Code dev server from source on Node 26.12.1, a plain MCP client over HTTP on Node 26.13.1 (no agent involved).

Logs or stack traces

v26.13.1
authorize -> 302, approval page /connect-agent
signed in, scope: orchestration:read
initialize -> server T3 Code 0.1.9
tools/list -> 68 tools (full reply saved)

--- t3_thread_update
"action": {"type":"string","enum":["rename","regenerate_title"]}
"title": {"type":"string"}
"clientRequestId": {"type":"string"}

--- delegate_task
"mode": {"type":"string","enum":["async","wait"],"description":"Default 'async'. 'wait' only if this turn needs the result. A question or approval ends the wait."}
"clientRequestId": {"type":"string"}

--- t3_thread_send
"threadId": {"type":"string"}
"clientRequestId": {"type":"string"}

Screenshots, recordings, or supporting files

Workaround

None that I found.

A fix is in #23285.