diff --git a/compiler/builtins/docs/Str.roc b/compiler/builtins/docs/Str.roc
index 159beb0e10..d403ad888f 100644
--- a/compiler/builtins/docs/Str.roc
+++ b/compiler/builtins/docs/Str.roc
@@ -433,37 +433,33 @@ toDec : Str -> Result Dec [ InvalidDec ]*
 
 ## If the string represents a valid number, return that number.
 ##
-## The exact number type to look for will be inferred from usage. Here's an
-## example where the `Err` branch matches `Integer Signed64`, which causes this to
-## parse an [I64] because [I64] is defined as `I64 : Num [ Integer [ Signed64 ] ]`.
+## The exact number type to look for will be inferred from usage.
+## In the example below, the usage of I64 in the type signature will require that type instead of (Num *).
 ##
-## >>> when Str.toNum "12345" is
-## >>>     Ok i64 -> "The I64 was: \(i64)"
-## >>>     Err (ExpectedNum (Integer Signed64)) -> "Not a valid I64!"
+## >>> strToI64 : Str -> Result I64 [ InvalidNumStr ]*
+## >>> strToI64 = \inputStr ->
+## >>>     Str.toNum inputStr
 ##
 ## If the string is exactly `"NaN"`, `"∞"`, or `"-∞"`, they will be accepted
 ## only when converting to [F64] or [F32] numbers, and will be translated accordingly.
 ##
 ## This never accepts numbers with underscores or commas in them. For more
 ## advanced options, see [parseNum].
-## TODO use `InvalidStr` or `ExpectedNum a` error
-toNum : Str -> Result (Num a) {}
+toNum : Str -> Result (Num *) [ InvalidNumStr ]*
 
 ## If the string begins with an [Int] or a [finite](Num.isFinite) [Frac], return
 ## that number along with the rest of the string after it.
 ##
-## The exact number type to look for will be inferred from usage. Here's an
-## example where the `Err` branch matches `Float Binary64`, which causes this to
-## parse an [F64] because [F64] is defined as `F64 : Num [ Fraction [ Float64 ] ]`.
+## The exact number type to look for will be inferred from usage.
+## In the example below, the usage of Float64 in the type signature will require that type instead of (Num *).
 ##
-## >>> when Str.parseNum input {} is
-## >>>     Ok { val: f64, rest } -> "The F64 was: \(f64)"
-## >>>     Err (ExpectedNum (Fraction Float64)) -> "Not a valid F64!"
+## >>> parseFloat64 : Str -> Result { val: Float64, rest: Str } [ InvalidNumStr ]*
+## >>>     Str.parseNum input {}
 ##
 ## If the string begins with `"NaN"`, `"∞"`, and `"-∞"` (which do not represent
 ## [finite](Num.isFinite) numbers), they will be accepted only when parsing
 ## [F64] or [F32] numbers, and translated accordingly.
-# parseNum : Str, NumParseConfig -> Result { val : Num a, rest : Str } [ ExpectedNum a ]*
+# parseNum : Str, NumParseConfig -> Result { val : Num *, rest : Str } [ InvalidNumStr ]*
 
 ## Notes:
 ## * You can allow a decimal mark for integers; they'll only parse if the numbers after it are all 0.
diff --git a/compiler/can/src/builtins.rs b/compiler/can/src/builtins.rs
index aeb21f83f2..9030c9f708 100644
--- a/compiler/can/src/builtins.rs
+++ b/compiler/can/src/builtins.rs
@@ -1324,7 +1324,7 @@ fn str_trim_right(symbol: Symbol, var_store: &mut VarStore) -> Def {
     lowlevel_1(symbol, LowLevel::StrTrimRight, var_store)
 }
 
-/// Str.toNum : Str -> Result (Num a) {}
+/// Str.toNum : Str -> Result (Num *) [ InvalidNumStr ]*
 fn str_to_num(symbol: Symbol, var_store: &mut VarStore) -> Def {
     lowlevel_1(symbol, LowLevel::StrToNum, var_store)
 }