A tool or operation seems to have become unavailable

This server's tool surface is static: describe, the verb tools (read, create, update, delete, act), and feedback are always registered, and every operation the docs list is always executable through the verb tools — nothing is exposed conditionally or withdrawn mid-session. If you could call something earlier in this conversation and now apparently cannot, the gap is in the connection between your client and this server, not a permission or capability change here.

What to do, in order:

1. Retry on a fresh turn — in some clients the set of callable tools is re-established per message, and a transient discovery failure heals on the next one.
2. Re-call describe() on the operation's path to confirm the operation still exists (it will).
3. If you still cannot invoke the verb tools, say so plainly and suggest the user reconnect this connector or continue in a new conversation.
4. Never report the action as done when it did not run, and never conclude "the server doesn't support this" — state what you observed instead.