Cargo Features

[dependencies]
pallet-transaction-payment-rpc-runtime-api = { version = "38.0.0", default-features = false, features = ["std"] }
default = std

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

std default

Enables std of parity-scale-codec, pallet-transaction-payment, sp-api, sp-runtime, and sp-weights

pallet-transaction-payment-rpc-runtime-api has 2 features without comments.