Document the reasons why the returned promise might fail

index.d.ts

@@ -268,6 +268,16 @@ declare namespace execa {
 		extends ExecaReturnBase<StdoutErrorType> {
 	}
 
+	/**
+	Result of a child process execution. On success this is a plain object. On failure this is also an `Error` instance.
+
+	The child process fails when:
+	- its exit code is not `0`
+	- it was killed with a signal
+	- timing out
+	- being canceled
+	- there's not enough memory or there are already too many child processes
+	*/
 	interface ExecaReturnValue<StdoutErrorType = string>
 		extends ExecaSyncReturnValue<StdoutErrorType> {
 		/**

readme.md

@@ -200,6 +200,13 @@ Type: `object`
 
 Result of a child process execution. On success this is a plain object. On failure this is also an `Error` instance.
 
+The child process [fails](#failed) when:
+- its [exit code](#exitcode) is not `0`
+- it was [killed](#killed) with a [signal](#signal)
+- [timing out](#timedout)
+- [being canceled](#iscanceled)
+- there's not enough memory or there are already too many child processes
+
 #### command
 
 Type: `string`