The client says it cannot sign in, or every request gets "Authentication required"
The web server may be dropping the Authorization header. Click Check on MCP Connections. If it reports that the header does not reach Omeka, see Installation for the line to add to .htaccess. Meanwhile an API key can go in the address: https://your-site/mcp?key=YOUR_API_KEY.
"The access token is invalid, expired or revoked"
The app was disconnected, or its sign-in expired and could not be renewed. Sign in again from the app (in Claude Code: /mcp, then Authenticate).
The Claude or ChatGPT app cannot connect
These apps connect from their own servers: the site must use HTTPS with a valid certificate and be reachable from the internet. Sites on a local or private network work only with Claude Code and Codex on the same network.
The editing tools are missing
They are hidden when the plugin is in read-only mode, when you connected with read-only access (the Create and edit box unticked on the consent page), and when your role cannot add items (researchers). Reconnect with edit access, or ask an administrator.
"You do not have permission to …"
Omeka's permissions apply to every change: contributors edit only their own items, and only Super Users change settings, the navigation and themes.
"Unknown field"
Fields are named "Element Set:Element", such as Dublin Core:Title or Item Type Metadata:Transcription; Dublin Core fields also as dcterms terms (dcterms:date). The message suggests close matches; search_elements lists them all. "Item Type Metadata" fields must belong to the item's item type (get_item_type).
"This installation does not let AI assistants make resources public"
Visibility of new records is set to "Always private". A staff member publishes records in the admin.
A file could not be added from a web address
The server downloads it while the tool runs. Check that the address points at the file itself, not a page about it, and that the file type is allowed under Settings > Security. Large files are better uploaded from your computer with request_upload.
A tool reports an internal error
Details go to Omeka's error log (application/logs/errors.log with log.errors on in application/config/config.ini).