OAuth against the vendor means the token belongs to the connection, not to whatever client you happened to use, and revoking it in one place actually revokes it. For a document store holding contracts and statements, that boundary is worth more than any tool in the list. Dynamic registration means you get it without filing a developer application first.
PdfAssistant's hosted endpoint, connected to the same account you use in their web app. Their own pitch for it is that the credentials stay with them and are never handed to the AI platform.
Your document library reachable from the conversation, so an assistant can read and answer against files you have already uploaded rather than needing them re-attached each time.
OAuth 2.0 with dynamic client registration — a compliant client discovers the authorisation server itself. A paid plan is needed; the integration is included on every paid tier rather than sold separately.
Paste a URL, then authorize — add the endpoint to your client, then approve the OAuth consent screen