Cargo Features

[dependencies]
frame-system-rpc-runtime-api = { version = "31.0.0", default-features = false, features = ["std"] }
default = std

The std feature is set by default whenever frame-system-rpc-runtime-api is added without default-features = false somewhere in the dependency tree.

std default

Enables std of parity-scale-codec and sp-api

frame-system-rpc-runtime-api has 2 features without comments.