PDF-Toolkit extension shown as installed/active in Claude Desktop (Mac) but not exposed as a usable tool in chat

[giopublic]

Environment

App: Claude Desktop for Mac — version 1.22209.0 (77c938), build date 2026-07-16T05:39:45.000Z
OS: macOS 26.5.2 (25F84)
Extension: PDF Tools – Fill, Sign, Merge, Split, Extract — version 0.8.6
Extension status: Installed and shown as active in the Claude Desktop extensions panel

Description
The PDF-Toolkit extension (v0.8.6) is installed and appears as active in the Claude Desktop extensions settings. However, when starting a conversation, Claude reports that the tool is not available among the connectors/tools it can actually call.
Specifically, Claude replied:

"I just re-checked the full list of tools available in this conversation, and there is nothing called 'PDF Tools', 'PDF-Toolkit', or similar among the active connectors/extensions."

Steps to reproduce

Install and enable the PDF Tools – Fill, Sign, Merge, Split, Extract extension (v0.8.6) in Claude Desktop for Mac (v1.22209.0).
Confirm it shows as active in the extensions panel.
Start a new chat and ask Claude to use PDF-Toolkit on a local file.
Claude states the tool is not present in its available tool list for that conversation.

Troubleshooting already attempted

Disabled and re-enabled the extension — no change.
Fully reinstalled the extension from the connectors menu (it showed a "+" as not-yet-installed, then was reinstalled) — still not detected in the active conversation.
Started new conversations after each of the above steps — Claude still does not detect/expose the tool.

Expected behavior
When an extension is shown as installed and active in Claude Desktop, it should be exposed as a callable tool within the chat session, or the UI should clearly indicate why it isn't available (e.g., pending activation, permission scope needed, requires app restart, etc.).
Actual behavior
The extension is listed as active in settings (v0.8.6), but is completely absent from the tools Claude can see/call during the conversation, with no error or explanation shown to the user, even after reinstalling and starting fresh conversations.

[giopublic]

Additional observation: intermittent tool availability within the same conversation thread
Confirming the reported behavior with a concrete in-session reproduction. Within a single, unbroken conversation thread in Claude Desktop, the extension's tools transitioned from "available and responding" to "not found."
Sequence observed:

First calls (same conversation, earlier turn): pdf-viewer:list_pdfs and pdf-viewer:display_pdf were both invoked successfully. list_pdfs returned its informational message about remote HTTPS PDFs (no local files listed). display_pdf on a dummy path (/test.pdf) returned an application-level error: Local file not in allowed list: /test.pdf with Allowed directories: empty — i.e., the tool was reachable and executing, just misconfigured (empty allowlist despite directories being set in the extension's config panel).
Later calls (same conversation thread): Two subsequent calls to pdf-viewer:list_pdfs (with and without a directory argument) both returned a system-level error instead: Tool 'pdf-viewer:list_pdfs' not found. Did you mean: view? Use the exact name shown here.

Between these calls, I disabled/re-enabled the extension, restarted Claude Desktop, and restarted my Mac — yet the tool still regressed from "reachable with a config-level error" to "not found," within the same conversation thread. So even a full app + OS restart plus a toggle of the extension did not produce stable tool exposure — the outcome (present vs. missing) still appears inconsistent across calls within one session.
Environment: same as reported above — Claude Desktop for Mac v1.22209.0 (77c938), macOS 26.5.2 (25F84), PDF Tools extension v0.8.6, shown as active in the extensions panel throughout.

[silverstein]

Thank you for the detailed in-session follow-up. We confirmed one concrete upstream problem that can suppress tools: the v0.8.6 display name can make generated MCP tool identifiers exceed the platform limit. The short-name fix is now merged in #45 (82c4837) and will be included in the next package. I am keeping this issue open: your observation that tools became unavailable after previously executing in the same thread may indicate a separate Claude Desktop lifecycle/host problem. We will request a retest against the packaged fix and continue investigating if availability still changes within a session.