Problem Statement/Rationale

When a placeholder code into aggregation pipeline is inserted as part of Atlas Search templates in Search Tester workflow , a confusing error is displayed: 

It's not clear what is experimental syntax that Compass/Atlas is complaining about 

Please be sure to attach relevant logs with any sensitive data redacted.
How to retrieve logs for: Compass; Shell

Steps to Reproduce

How could an engineer replicate the issue you’re reporting?

create default search index on a database, copy paste code in Aggregation pipeline: 

[
{
$searchMeta: {
index: "default",
facet: {
facets: {
facet_name: { type: "string", path: "<field-path>", numBuckets: <integer>, },
},
},
},
},
]

Expected Results

Expected error to tell me to enter an integer

Actual Results

What do you observe is happening?

Confusing error about experimental syntax

Additional Notes

Any additional information that may be useful to include.