Could not find operation StartInstances for version 2016-11-15

I'm trying start instance remotely in code, because all I need are two apis StartInstances and StopInstances so don't really want to install the sdk.

So I followed the example here: https://docs.aws.amazon.com/general/latest/gr/sigv4-signed-request-examples.html#sig-v4-examples-post

replaced with my own credentials and the parameters listed here: https://docs.aws.amazon.com/AWSEC2/latest/APIReference/API_StartInstances.html

but i'm still getting this error: Could not find operation StartInstances for version 2016-11-15

Any idea why it's throwing this error?