DKIM public key for selector "1" of a domain: looks up 1._domainkey.<domain> (TXT, Cloudflare DoH) and parses v=, k=, key type, public-key length, testing flag and whether the key is revoked (empty p=). Confirms that mail signed with the 1 selector will verify. $0.01 per lookup.
https://dns.intel.rallylive.ca/dns/dkim/1