[BUG] Connected custom MCP connector tools not discoverable via tool_search in claude.ai chat

Preflight Checklist

• [x] I have searched existing issues and this hasn't been reported yet
• [x] This is a single bug report (please file separate reports for different bugs)
• [x] I am using the latest version of Claude Code

What's Wrong?

What's Wrong?

A connected custom MCP connector ("NextClaud", a remote FastMCP StreamableHTTP server behind a named Cloudflare tunnel) shows as connected with 133 tools in the claude.ai Connectors settings UI, but none of its tools can be found via tool_search inside an actual chat session. The connector is completely unusable in claude.ai chat, even though the server itself is healthy — a separate Claude Code session connecting directly to the same MCP server successfully loads all 133+ tools.

This points to a discrepancy between the connector-settings UI layer (which correctly shows "Connected" + full tool list) and the tool-discovery layer (tool_search) actually used inside a chat session.

What Should Happen?

What Should Happen?

tool_search should return the connector's tools when queried with relevant keywords or exact tool names, matching what the Connectors settings UI shows as available.

Error Messages/Logs

Error Messages/Logs

No error is shown to the user. tool_search simply returns zero results for this connector regardless of query — no error message, no timeout indication. Tools from other connected services (Gmail, Google Drive, Claude in Chrome) load normally via the same mechanism in the same session.

Steps to Reproduce

Steps to Reproduce

Connect a custom remote MCP connector via claude.ai → Settings → Connectors (in this case a FastMCP StreamableHTTP server at https://mcp.adrievanlith.nl/mcp, behind a named Cloudflare tunnel).
Confirm in the UI that it shows "Connected" with its full tool list (133 tools, e.g. collectives_get_collectives, collectives_create_page, etc.).
Start a new chat and ask Claude to use one of the connector's tools.
Claude calls tool_search with relevant keywords.
Expected: tools are returned and loaded. Actual: zero results, every time, for any query (connector name, generic keywords, exact tool names copied from the UI list).

Already tried, no effect on the result:

Tested in 3+ separate new chat sessions.
Fully disconnected and reconnected the connector (full OAuth re-registration), then tested again in a brand-new chat. No change.
Retried over several hours. Issue remains consistently reproducible.

Evidence the server/tunnel/auth are healthy: a separate Claude Code session, connecting to the same MCP server via a direct MCP config (not through the claude.ai connector layer), successfully loads 133+ tools from it. This indicates the FastMCP server, the named Cloudflare tunnel, and OAuth tokens are all functioning correctly — the bug appears isolated to claude.ai's in-chat tool-discovery for this connector.

Claude Model

None

Is this a regression?

Yes, this worked in a previous version

Last Working Version

_No response_

Claude Code Version

4.6

Platform

Anthropic API

Operating System

Windows

Terminal/Shell

Terminal.app (macOS)

Additional Information

MCP server: custom FastMCP StreamableHTTP server, reachable via named Cloudflare tunnel at mcp.adrievanlith.nl (migrated from a trycloudflare.com quick tunnel).
Connector shows 133 tools in Settings → Connectors → NextClaud, status "Connected".
This occurred during a period of broader platform instability (Anthropic status page showed a major incident regarding Claude Mythos 5 / Fable 5 access starting June 13, 2026, and a resolved elevated-error-rate incident on the Claude API on June 19, 2026). No confirmed causal link to this specific bug, but timing overlaps.
Impact: this fully blocks using the connector from claude.ai chat. The only working access path currently is a separate Claude Code session with a direct MCP config — a different workflow that isn't a substitute for chat-based use.

<img width="1982" height="1090" alt="Image" src="https://github.com/user-attachments/assets/99f29705-fae4-4b81-a260-c703332c1320" />