Every platform in this category has a wall of logos, and every wall has the same problem: a logo says somebody once wrote a file with that vendor's name at the top. It does not say whether a message has ever gone through it.
Each connector here carries one of three labels, and a build gate enforces them.
The three
Generally available. The path has been run against a real account. Connecting it and using it are the same thing.
Preview. We wrote the integration against the vendor's documentation and nobody has verified it against a paid account from this codebase. The shape is probably right. It has not been proven right.
Partner gated. Access needs a step we do not control: a signed agreement, an application review, an approval queue. The code may be complete and you still cannot use it until the vendor says yes.
The gate, and the rule that makes it work
A connector whose code carries a verify marker may not claim to be generally available. That check runs on every build.
The important half of the rule is subtler. The label is optional in the type, and leaving it out means generally available. So saying nothing is the cheapest way to break this rule, not a way to sidestep it, and the check is written to catch omission rather than only to catch a wrong word.
There is a history behind that. For months the rule forbade a status value the type had never accepted, which meant it could not possibly have fired against anything. It read like a working gate and was decorative. That is a more dangerous state than having no gate at all, because everybody stops looking.
What that means for the wall
It means our number looks worse than it could. Plenty of the connectors on the list say preview, and several say partner gated. We could delete a line from a few files and the whole wall would read generally available tomorrow, and nothing about the software would have changed.
The reason not to is straightforward. A buyer picks a platform partly on the connector they need, and if that connector turns out to be a file with a vendor's name at the top, they find out during implementation. Six that work beat fifty that say preview, and the only way to tell those apart from outside is if somebody labels them.