diff --git a/CONTRIBUTING.md b/CONTRIBUTING.md
index 69ebb3762..d426a7ef0 100644
--- a/CONTRIBUTING.md
+++ b/CONTRIBUTING.md
@@ -12,4 +12,4 @@ Apart from the conditions above, this repository follows the [ColPrac](https://g
 Its code is formatted using [Runic.jl](https://github.com/fredrikekre/Runic.jl).
 As part of continuous integration, a set of formal tests is run using [pre-commit](https://pre-commit.com/).
 We invite you to install pre-commit so that these checks are performed locally before you open or update a pull request.
-You can refer to the [dev guide](https://juliadiff.org/DifferentiationInterface.jl/DifferentiationInterface/dev/dev_guide/) for details on the package structure and the testing pipeline.
+You can refer to the relevant page of the development documentation for details on the package structure and the testing pipeline.
diff --git a/DifferentiationInterface/docs/make.jl b/DifferentiationInterface/docs/make.jl
index 49f39ad6c..791b048c5 100644
--- a/DifferentiationInterface/docs/make.jl
+++ b/DifferentiationInterface/docs/make.jl
@@ -35,7 +35,10 @@ makedocs(;
         ],
         "FAQ" => ["faq/limitations.md", "faq/differentiability.md"],
         "api.md",
-        "dev_guide.md",
+        "Development" => [
+            "dev/internals.md",
+            "dev/contributing.md",
+        ],
     ],
     plugins = [links],
 )
diff --git a/DifferentiationInterface/docs/src/api.md b/DifferentiationInterface/docs/src/api.md
index ac50ab1ab..108f1c03d 100644
--- a/DifferentiationInterface/docs/src/api.md
+++ b/DifferentiationInterface/docs/src/api.md
@@ -139,12 +139,8 @@ DifferentiationInterface.AutoForwardFromPrimitive
 DifferentiationInterface.AutoReverseFromPrimitive
 ```
 
-## Internals
+### Preparation type
 
-The following is not part of the public API.
-
-```@autodocs
-Modules = [DifferentiationInterface]
-Public = false
-Filter = t -> !(Symbol(t) in [:outer, :inner])
+```@docs
+DifferentiationInterface.Prep
 ```
diff --git a/DifferentiationInterface/docs/src/dev_guide.md b/DifferentiationInterface/docs/src/dev/contributing.md
similarity index 80%
rename from DifferentiationInterface/docs/src/dev_guide.md
rename to DifferentiationInterface/docs/src/dev/contributing.md
index 4538a1117..d7913193a 100644
--- a/DifferentiationInterface/docs/src/dev_guide.md
+++ b/DifferentiationInterface/docs/src/dev/contributing.md
@@ -1,4 +1,4 @@
-# Dev guide
+# Contributing
 
 This page is important reading if you want to contribute to DifferentiationInterface.jl.
 It is not part of the public API and the content below may become outdated, in which case you should refer to the source code as the ground truth.
@@ -7,26 +7,27 @@ It is not part of the public API and the content below may become outdated, in w
 
 The package is structured around 8 [operators](@ref Operators):
 
-  - [`derivative`](@ref)
-  - [`second_derivative`](@ref)
-  - [`gradient`](@ref)
-  - [`jacobian`](@ref)
-  - [`hessian`](@ref)
-  - [`pushforward`](@ref)
-  - [`pullback`](@ref)
-  - [`hvp`](@ref)
+- [`derivative`](@ref)
+- [`second_derivative`](@ref)
+- [`gradient`](@ref)
+- [`jacobian`](@ref)
+- [`hessian`](@ref)
+- [`pushforward`](@ref)
+- [`pullback`](@ref)
+- [`hvp`](@ref)
 
 Most operators have 4 variants, which look like this in the first order: `operator`, `operator!`, `value_and_operator`, `value_and_operator!`.
 
 ## New operator
 
 To implement a new operator for an existing backend, you need to write 5 methods: 1 for [preparation](@ref Preparation) and 4 corresponding to the variants of the operator (see above).
-For first-order operators, you may also want to support [in-place functions](@ref "Mutation and signatures"), which requires another 5 methods (defined on `f!` instead of `f`).
+For some operators, you will also need to support [in-place functions](@ref "Mutation and signatures"), which requires another 5 methods (defined on `f!` instead of `f`).
 
 The method `prepare_operator_nokwarg` must output a `prep` object of the correct type.
-For instance, `prepare_gradient(strict, f, backend, x)` must return a [`DifferentiationInterface.GradientPrep`](@ref).
-Assuming you don't need any preparation for said operator, you can use the trivial prep that are already defined, like `DifferentiationInterface.NoGradientPrep{SIG}`.
+For instance, `prepare_gradient_nokwarg(strict, f, backend, x)` must return a [`DifferentiationInterface.GradientPrep`](@ref).
+Assuming you don't need any preparation for said operator, you can use the trivial preparation types that are already defined, like `DifferentiationInterface.NoGradientPrep{SIG}`.
 Otherwise, define a custom struct like `MyGradientPrep{SIG} <: DifferentiationInterface.GradientPrep{SIG}` and put the necessary storage in there.
+Take inspiration from existing operators on how to enforce the signature `SIG`.
 
 ## New backend
 
@@ -36,10 +37,10 @@ Your AD package needs to be registered first.
 ### Core code
 
 In the main package, you should define a new struct `SuperDiffBackend` which subtypes [`ADTypes.AbstractADType`](@extref ADTypes), and endow it with the fields you need to parametrize your differentiation routines.
-You also have to define [`ADTypes.mode`](@extref) and [`DifferentiationInterface.inplace_support`](@ref) on `SuperDiffBackend`.
+You also have to define [`ADTypes.mode`](@extref), [`DifferentiationInterface.check_available`](@ref) and [`DifferentiationInterface.inplace_support`](@ref) on `SuperDiffBackend`.
 
 !!! info
-    
+
     In the end, this backend struct will need to be contributed to [ADTypes.jl](https://github.com/SciML/ADTypes.jl).
     However, putting it in the DifferentiationInterface.jl PR is a good first step for debugging.
 
@@ -47,7 +48,7 @@ In a [package extension](https://pkgdocs.julialang.org/v1/creating-packages/#Con
 The exact requirements depend on the differentiation mode you chose:
 
 | backend mode                                      | pushforward necessary | pullback necessary |
-|:------------------------------------------------- |:--------------------- |:------------------ |
+| :------------------------------------------------ | :-------------------- | :----------------- |
 | [`ADTypes.ForwardMode`](@extref ADTypes)          | yes                   | no                 |
 | [`ADTypes.ReverseMode`](@extref ADTypes)          | no                    | yes                |
 | [`ADTypes.ForwardOrReverseMode`](@extref ADTypes) | yes                   | yes                |
diff --git a/DifferentiationInterface/docs/src/dev/internals.md b/DifferentiationInterface/docs/src/dev/internals.md
new file mode 100644
index 000000000..3a18900b2
--- /dev/null
+++ b/DifferentiationInterface/docs/src/dev/internals.md
@@ -0,0 +1,9 @@
+# Internals
+
+The following names are not part of the public API.
+
+```@autodocs
+Modules = [DifferentiationInterface]
+Public = false
+Filter = t -> !(Symbol(t) in [:outer, :inner, :Prep, :AutoForwardFromPrimitive, :AutoReverseFromPrimitive])
+```
diff --git a/DifferentiationInterface/src/DifferentiationInterface.jl b/DifferentiationInterface/src/DifferentiationInterface.jl
index 32bfc4703..4a07e7301 100644
--- a/DifferentiationInterface/src/DifferentiationInterface.jl
+++ b/DifferentiationInterface/src/DifferentiationInterface.jl
@@ -129,6 +129,7 @@ export AutoSparse
 
 @public inner, outer
 @public AutoForwardFromPrimitive, AutoReverseFromPrimitive
+@public Prep
 
 include("init.jl")
 
diff --git a/DifferentiationInterface/src/utils/prep.jl b/DifferentiationInterface/src/utils/prep.jl
index 95ea16609..9285b9950 100644
--- a/DifferentiationInterface/src/utils/prep.jl
+++ b/DifferentiationInterface/src/utils/prep.jl
@@ -1,3 +1,11 @@
+"""
+    Prep
+
+Abstract supertype for all preparation results (outputs of `prepare_operator` functions).
+
+!!! warning
+    The public API does not make any guarantees about the type parameters or field layout of `Prep`, the only guarantee is that this type exists.
+"""
 abstract type Prep{SIG} end
 
 """
diff --git a/DifferentiationInterface/test/Core/Internals/prep.jl b/DifferentiationInterface/test/Core/Internals/prep.jl
new file mode 100644
index 000000000..12762442d
--- /dev/null
+++ b/DifferentiationInterface/test/Core/Internals/prep.jl
@@ -0,0 +1,14 @@
+using DifferentiationInterface: Prep
+using InteractiveUtils: subtypes
+using Test
+
+@test subtypes(Prep) == [
+    DifferentiationInterface.DerivativePrep,
+    DifferentiationInterface.GradientPrep,
+    DifferentiationInterface.HVPPrep,
+    DifferentiationInterface.HessianPrep,
+    DifferentiationInterface.JacobianPrep,
+    DifferentiationInterface.PullbackPrep,
+    DifferentiationInterface.PushforwardPrep,
+    DifferentiationInterface.SecondDerivativePrep,
+]
diff --git a/DifferentiationInterface/test/Project.toml b/DifferentiationInterface/test/Project.toml
index 5e06b62f7..20d7f55af 100644
--- a/DifferentiationInterface/test/Project.toml
+++ b/DifferentiationInterface/test/Project.toml
@@ -5,6 +5,7 @@ ComponentArrays = "b0b7db55-cfe3-40fc-9ded-d10e2dbeff66"
 DataFrames = "a93c6f00-e57d-5684-b7b6-d8193f3e46c0"
 Dates = "ade2ca70-3891-5945-98fb-dc099432e06a"
 ExplicitImports = "7d51a73a-1435-4ff3-83d9-f097790105c7"
+InteractiveUtils = "b77e0a4c-d291-57a0-90e8-8db25a27a240"
 JET = "c3a54625-cd67-489e-a8e7-0a5a0ff4e31b"
 JLArrays = "27aeb0d3-9eb9-45fb-866b-73c2ecf80fcb"
 LinearAlgebra = "37e2e46d-f89d-539d-b4ee-838fcccc9c8e"
@@ -23,6 +24,7 @@ ComponentArrays = "0.15.27"
 DataFrames = "1.7.0"
 Dates = "1"
 ExplicitImports = "1.10.1"
+InteractiveUtils = "1"
 JET = "0.9,0.10"
 JLArrays = "0.2.0"
 Pkg = "1"