diff --git a/src/GeometryOps.jl b/src/GeometryOps.jl
index 9e19dd553..b5d06507d 100644
--- a/src/GeometryOps.jl
+++ b/src/GeometryOps.jl
@@ -33,6 +33,7 @@ include("methods/polygonize.jl")
 include("methods/barycentric.jl")
 include("methods/equals.jl")
 
+include("transformations/extent.jl")
 include("transformations/flip.jl")
 include("transformations/simplify.jl")
 include("transformations/reproject.jl")
diff --git a/src/primitives.jl b/src/primitives.jl
index 1ca4e0224..9a9ea8127 100644
--- a/src/primitives.jl
+++ b/src/primitives.jl
@@ -1,10 +1,19 @@
+const THREADED_KEYWORD = "- `threaded`: `true` or `false`. Whether to use multithreading. Defaults to `false`."
+const CRS_KEYWORD = "- `crs`: The CRS to attach to geometries. Defaults to `nothing`."
+const CALC_EXTENT_KEYWORD = "- `calc_extent`: `true` or `false`. Whether to calculate the extent. Defaults to `false`."
+
+const APPLY_KEYWORDS = """
+$THREADED_KEYWORD
+$CRS_KEYWORD
+$CALC_EXTENT_KEYWORD
+"""
 
 # # Primitive functions
 
 # This file mainly defines the [`apply`](@ref) function.
 
 """
-    apply(f, target::Type{<:AbstractTrait}, obj; crs)
+    apply(f, target::Type{<:AbstractTrait}, obj; kw...)
 
 Reconstruct a geometry or feature using the function `f` on the `target` trait.
 
@@ -12,7 +21,11 @@ Reconstruct a geometry or feature using the function `f` on the `target` trait.
 
 The result is an functionally similar geometry with values depending on `f`
 
-# Flipped point the order in any feature or geometry, or iterables of either:
+$APPLY_KEYWORDS
+
+# Example
+
+Flipped point the order in any feature or geometry, or iterables of either:
 
 ```juia
 import GeoInterface as GI
diff --git a/src/transformations/extent.jl b/src/transformations/extent.jl
index 98051bf6e..9055de135 100644
--- a/src/transformations/extent.jl
+++ b/src/transformations/extent.jl
@@ -1,24 +1,17 @@
 """
     embed_extent(obj)
 
-Recursively wrap the object with a `GeoInterface.Wrappers` geometry,
+Recursively wrap the object with a GeoInterface.jl geometry,
 calculating and adding an `Extents.Extent` to all objects.
 
-This can improve performance when extents need to be checked multiple times.
-"""
-embed_extent(x; kw...) = apply(AbstractTrait, x; kw...)
+This can improve performance when extents need to be checked multiple times,
+such when needing to check if many points are in geometries, and using their extents
+as a quick filter for obviously exterior points.
+
+# Keywords
 
-extent_applicator(x) = extent_applicator(trait(x), x)
-extent_applicator(::Nothing, xs::AbstractArray) = embed_extent.(xs)
-extent_applicator(::Union{AbstractCurveTrait,MultiPointTrait}, point) = point
-    
-function extent_applicator(trait::AbstractGeometryTrait, geom)
-    children_with_extents = map(GI.getgeom(geom)) do g
-        embed_extent(g)
-    end
-    wrapper_type = GI.geointerface_geomtype(trait)
-    extent = GI.extent(wrapper_type(children_with_extents))
-    return wrapper_type(children_with_extents, extent)
-end
-extent_applicator(::PointTrait, point) = point
-extent_applicator(::PointTrait, point) = point
+$THREADED_KEYWORD
+$CRS_KEYWORD
+"""
+embed_extent(x; threaded=false, crs=nothing) = 
+    apply(identity, GI.PointTrait, x; calc_extent=true, threaded, crs)
diff --git a/src/transformations/flip.jl b/src/transformations/flip.jl
index e746456bb..eee3bed42 100644
--- a/src/transformations/flip.jl
+++ b/src/transformations/flip.jl
@@ -9,6 +9,10 @@
 Swap all of the x and y coordinates in obj, otherwise
 keeping the original structure (but not necessarily the
 original type).
+
+## Keywords 
+
+$APPLY_KEYWORDS
 """
 function flip(geom; kw...) 
     if _is3d(geom)
diff --git a/src/transformations/reproject.jl b/src/transformations/reproject.jl
index dd61c15bd..d59cbd92f 100644
--- a/src/transformations/reproject.jl
+++ b/src/transformations/reproject.jl
@@ -30,9 +30,10 @@ needed if it is not retreivable from the geometry with `GeoInterface.crs(geometr
 
 ## Keywords
 
--`always_xy`: force x, y coordinate order, `true` by default.
+- `always_xy`: force x, y coordinate order, `true` by default.
     `false` will expect and return points in the crs coordinate order.
--`time`: the time for the coordinates. `Inf` by default.
+- `time`: the time for the coordinates. `Inf` by default.
+$APPLY_KEYWORDS
 """
 function reproject(geom;
     source_crs=nothing, target_crs=nothing, transform=nothing, kw...
diff --git a/src/transformations/simplify.jl b/src/transformations/simplify.jl
index ee095f5b0..1dd2fb55b 100644
--- a/src/transformations/simplify.jl
+++ b/src/transformations/simplify.jl
@@ -22,6 +22,7 @@ abstract type SimplifyAlg end
 
 const SIMPLIFY_ALG_KEYWORDS = """
 ## Keywords
+
 - `ratio`: the fraction of points that should remain after `simplify`. 
     Useful as it will generalise for large collections of objects.
 - `number`: the number of points that should remain after `simplify`.
@@ -48,7 +49,7 @@ end
 
 """
     simplify(obj; kw...)
-    simplify(::SimplifyAlg, obj)
+    simplify(::SimplifyAlg, obj; kw...)
 
 Simplify a geometry, feature, feature collection, 
 or nested vectors or a table of these.
@@ -62,6 +63,14 @@ listed in order of increasing quality but decreaseing performance.
 The default behaviour is `simplify(DouglasPeucker(; kw...), obj)`.
 Pass in other [`SimplifyAlg`](@ref) to use other algorithms.
 
+# Keywords
+
+$APPLY_KEYWORDS
+
+Keywords for DouglasPeucker are allowed when no algorithm is specified:
+
+$SIMPLIFY_ALG_KEYWORDS
+
 # Example
 
 Simplify a polygon to have six points:
@@ -99,8 +108,8 @@ GI.npoint(simple)
 6
 ```
 """
-simplify(data; calc_extent=false, threaded=false, kw...) =
-    _simplify(DouglasPeucker(; kw...), data; calc_extent, threaded)
+simplify(data; calc_extent=false, threaded=false, crs=nothing, kw...) =
+    _simplify(DouglasPeucker(; kw...), data; calc_extent, threaded, crs)
 simplify(alg::SimplifyAlg, data; kw...) = _simplify(alg, data; kw...)
 
 function _simplify(alg::SimplifyAlg, data; kw...)
diff --git a/src/transformations/tuples.jl b/src/transformations/tuples.jl
index ff82b781b..fe1bf0026 100644
--- a/src/transformations/tuples.jl
+++ b/src/transformations/tuples.jl
@@ -3,7 +3,14 @@
 """
     tuples(obj)
 
-Convert all points on obj to `Tuple`s.
+Convert all points in `obj` to `Tuple`s, wherever the are nested.
+
+Returns a similar object or collection of objects using GeoInterface.jl
+geometries wrapping `Tuple` points.
+
+# Keywords
+
+$APPLY_KEYWORDS
 """
 function tuples(geom; kw...) 
     if _is3d(geom)
diff --git a/test/runtests.jl b/test/runtests.jl
index ee2065017..88e71bec3 100644
--- a/test/runtests.jl
+++ b/test/runtests.jl
@@ -23,6 +23,7 @@ const GO = GeometryOps
     @testset "Signed Area" begin include("methods/signed_area.jl") end
     @testset "Overlaps" begin include("methods/overlaps.jl") end
     # Transformations
+    @testset "Embed Extent" begin include("transformations/extent.jl") end
     @testset "Reproject" begin include("transformations/reproject.jl") end
     @testset "Flip" begin include("transformations/flip.jl") end
     @testset "Simplify" begin include("transformations/simplify.jl") end
diff --git a/test/transformations/extent.jl b/test/transformations/extent.jl
new file mode 100644
index 000000000..beadeba9f
--- /dev/null
+++ b/test/transformations/extent.jl
@@ -0,0 +1,16 @@
+using Test
+ 
+import GeoInterface as GI
+import GeometryOps as GO
+using GeoInterface: Extents
+
+@testset "embed_extent" begin
+    poly = GI.Polygon([GI.LinearRing([(1, 2), (3, 4), (5, 6), (1, 2)]), 
+                       GI.LinearRing([(3, 4), (5, 6), (6, 7), (3, 4)])])
+
+    ext_poly = GO.embed_extent(poly)
+    lr1, lr2 = GI.getgeom(ext_poly)
+    @test ext_poly.extent == Extents.Extent(X=(1, 6), Y=(2, 7))
+    @test lr1.extent == Extents.Extent(X=(1, 5), Y=(2, 6))
+    @test lr2.extent == Extents.Extent(X=(3, 6), Y=(4, 7))
+end