Search API annotations for queries and results
Queries are processed internally. For example the query is tokenized, lemmatized, word breaker is applied, synonyms, white-/blacklisting, etc. To understand what happens with a query we have to scour through ULS logs today.
The search API should include an annotation list that explains each step and modification that is done to a query. Similarly all modifications done to results should also be annotated. This was a feature in FAST ESP prior to SP2013.
The API can be extended with annotations without breaking compatibility with the current API. It will be an invaluable tool for developers and admins as part of debugging. Furthermore it can be used by applications that use the search API. For example by explaining to end users that what kinds of modifications were done to their query.