I would say yes. If you're writing that YML by hand, and that YML doesn't have extensions that provides control-flow (e.g. CloudFormation's if syntax), then you

I would say yes. If you're writing that YML by hand, and that YML doesn't have extensions that provides control-flow (e.g. CloudFormation's if syntax), then you're writing something declarative. If you're using an imperative language, and you're using control-flow, then you're using that tool in an imperative way. It doesn't make sense to define the attributes of a tool by its artifacts. If we applied that logic across the board then Haskell isn't a purely functional language because it eventually gets compiled to machine code which is imperative. What matters is the source, not the artifact. In the case of Pulumi you are using imperative languages, so Pulumi is effectively imperative, although it can technically be considered declarative when you consider the Pulumi runtime. If Pulumi had support for a declarative language, then I would consider it a declarative tool.