Directory Assistants fetching for a user

Meta-ExternalFetcher Agent

Acts for a person. Operated by meta.

Identity: Signs its requests (Web Bot Auth).

How to recognise it

Signed requests: Signature-Agent from www.meta.com, keys at https://www.meta.com/.well-known/http-message-signatures-directory
User agent contains meta-externalfetcher

With Double Agent

Sessions from Meta-ExternalFetcher are labelled agent with agent_id: meta.externalfetcher, and tagged in your analytics. Nothing is blocked unless you choose to. Install: https://doubleagent.so/install.md

Source: https://developers.facebook.com/docs/sharing/webmasters/web-crawlers · Operator docs: https://developers.facebook.com/docs/sharing/webmasters/web-crawlers