From 97e23d6589c791873ce89654107dede1e2154826 Mon Sep 17 00:00:00 2001
From: Aayush Sabharwal <aayush.sabharwal@gmail.com>
Date: Mon, 11 Aug 2025 05:50:52 +0530
Subject: [PATCH 01/12] refactor: make `AbstractSystem` public, add docs

---
 docs/src/API/System.md | 1 +
 src/ModelingToolkit.jl | 3 ++-
 2 files changed, 3 insertions(+), 1 deletion(-)

diff --git a/docs/src/API/System.md b/docs/src/API/System.md
index 379e7fa19b..7620014b19 100644
--- a/docs/src/API/System.md
+++ b/docs/src/API/System.md
@@ -7,6 +7,7 @@ optimizations).
 
 ```@docs
 System
+ModelingToolkit.AbstractSystem
 ```
 
 ## Utility constructors
diff --git a/src/ModelingToolkit.jl b/src/ModelingToolkit.jl
index 1dbf9d37dd..0a7b999cc3 100644
--- a/src/ModelingToolkit.jl
+++ b/src/ModelingToolkit.jl
@@ -134,7 +134,7 @@ in a non-breaking release. Usage of these arguments is not advised.
 """
 $(TYPEDEF)
 
-TODO
+Abstract supertype of all system types. Any custom system types must subtype this.
 """
 abstract type AbstractSystem end
 # Solely so that `ODESystem` can be deprecated and still act as a valid type.
@@ -336,6 +336,7 @@ export DynamicOptSolution
 @public is_diff_equation, Equality, linearize_symbolic, reorder_unknowns
 @public similarity_transform, inputs, outputs, bound_inputs, unbound_inputs, bound_outputs
 @public unbound_outputs, is_bound
+@public AbstractSystem
 
 for prop in [SYS_PROPS; [:continuous_events, :discrete_events]]
     getter = Symbol(:get_, prop)

From d4f4af628af4c82c75d4ab6fdaf2370f396e6be0 Mon Sep 17 00:00:00 2001
From: Aayush Sabharwal <aayush.sabharwal@gmail.com>
Date: Mon, 11 Aug 2025 06:05:13 +0530
Subject: [PATCH 02/12] refactor: document `check` keyword flags, mark as
 public

---
 docs/src/API/System.md | 14 ++++++++++++++
 src/ModelingToolkit.jl |  2 +-
 src/utils.jl           | 22 ++++++++++++++++++++++
 3 files changed, 37 insertions(+), 1 deletion(-)

diff --git a/docs/src/API/System.md b/docs/src/API/System.md
index 7620014b19..b5dd08bdc7 100644
--- a/docs/src/API/System.md
+++ b/docs/src/API/System.md
@@ -186,3 +186,17 @@ ModelingToolkit.is_bound
 ```@docs
 debug_system
 ```
+
+## Input validation
+
+The following values can be passed to the `check` keyword of `System` to toggle validation
+of input. Flags can be combined with bitwise `|` and `&`.
+
+```@docs
+ModelingToolkit.CheckAll
+ModelingToolkit.CheckNone
+ModelingToolkit.CheckComponents
+ModelingToolkit.CheckUnits
+```
+
+These can also be used by custom `AbstractSystem` subtypes.
diff --git a/src/ModelingToolkit.jl b/src/ModelingToolkit.jl
index 0a7b999cc3..800ae899da 100644
--- a/src/ModelingToolkit.jl
+++ b/src/ModelingToolkit.jl
@@ -336,7 +336,7 @@ export DynamicOptSolution
 @public is_diff_equation, Equality, linearize_symbolic, reorder_unknowns
 @public similarity_transform, inputs, outputs, bound_inputs, unbound_inputs, bound_outputs
 @public unbound_outputs, is_bound
-@public AbstractSystem
+@public AbstractSystem, CheckAll, CheckNone, CheckComponents, CheckUnits
 
 for prop in [SYS_PROPS; [:continuous_events, :discrete_events]]
     getter = Symbol(:get_, prop)
diff --git a/src/utils.jl b/src/utils.jl
index d028d4ed18..8ec9def5e9 100644
--- a/src/utils.jl
+++ b/src/utils.jl
@@ -88,9 +88,31 @@ function readable_code(expr)
 end
 
 # System validation enums
+"""
+    const CheckNone
+
+Value that can be provided to the `check` keyword of `System` to disable checking of input.
+"""
 const CheckNone = 0
+"""
+    const CheckAll
+
+Value that can be provided to the `check` keyword of `System` to enable all input
+validation.
+"""
 const CheckAll = 1 << 0
+"""
+    const CheckComponents
+
+Value that can be provided to the `check` keyword of `System` to only enable checking of
+basic components of the system, such as equations, variables, etc.
+"""
 const CheckComponents = 1 << 1
+"""
+    const CheckUnits
+
+Value that can be provided to the `check` keyword of `System` to enable checking of units.
+"""
 const CheckUnits = 1 << 2
 
 function check_independent_variables(ivs)

From 42034e9642c86966410579def4eb271fc37e503a Mon Sep 17 00:00:00 2001
From: Aayush Sabharwal <aayush.sabharwal@gmail.com>
Date: Mon, 11 Aug 2025 06:08:01 +0530
Subject: [PATCH 03/12] refactor: mark common `t*` and `D*` as public

---
 docs/src/API/model_building.md | 23 +++++++++++++++++++++++
 src/ModelingToolkit.jl         |  1 +
 2 files changed, 24 insertions(+)

diff --git a/docs/src/API/model_building.md b/docs/src/API/model_building.md
index cbdf72edae..28069b535e 100644
--- a/docs/src/API/model_building.md
+++ b/docs/src/API/model_building.md
@@ -3,6 +3,29 @@
 This page lists functionality and utilities related to building hierarchical models. It is
 recommended to read the page on the [`System`](@ref System_type) before this.
 
+## Common definitions of `t` and `D`
+
+ModelingToolkit provides common definitions for the independent variable `t` (time) and the
+derivative with respect to it `D`.
+
+```@docs
+ModelingToolkit.t_nounits
+ModelingToolkit.D_nounits
+ModelingToolkit.t
+ModelingToolkit.D
+ModelingToolkit.t_unitful
+ModelingToolkit.D_unitful
+```
+
+Users are recommended to use the appropriate common definition in their models. The required
+definitions can be imported with convenient aliased names. For example:
+
+```julia
+using ModelingToolkit: t_nounits as t, D_nounits as D
+```
+
+Allows using `t` and `D` to refer to `t_nounits` and `D_nounits` respectively.
+
 ## Hierarchical model composition
 
 The `System` data structure can represent a tree-like hierarchy of systems for building models
diff --git a/src/ModelingToolkit.jl b/src/ModelingToolkit.jl
index 800ae899da..0a225e4e12 100644
--- a/src/ModelingToolkit.jl
+++ b/src/ModelingToolkit.jl
@@ -337,6 +337,7 @@ export DynamicOptSolution
 @public similarity_transform, inputs, outputs, bound_inputs, unbound_inputs, bound_outputs
 @public unbound_outputs, is_bound
 @public AbstractSystem, CheckAll, CheckNone, CheckComponents, CheckUnits
+@public t, D, t_nounits, D_nounits, t_unitful, D_unitful
 
 for prop in [SYS_PROPS; [:continuous_events, :discrete_events]]
     getter = Symbol(:get_, prop)

From 9cfba5b517831c06e5a520f4b1023344b34b4921 Mon Sep 17 00:00:00 2001
From: Aayush Sabharwal <aayush.sabharwal@gmail.com>
Date: Mon, 11 Aug 2025 06:20:25 +0530
Subject: [PATCH 04/12] refactor: mark `SymbolicContinuousCallback`,
 `SymbolicDiscreteCallback` as public

---
 src/ModelingToolkit.jl | 1 +
 1 file changed, 1 insertion(+)

diff --git a/src/ModelingToolkit.jl b/src/ModelingToolkit.jl
index 0a225e4e12..98a9267e57 100644
--- a/src/ModelingToolkit.jl
+++ b/src/ModelingToolkit.jl
@@ -338,6 +338,7 @@ export DynamicOptSolution
 @public unbound_outputs, is_bound
 @public AbstractSystem, CheckAll, CheckNone, CheckComponents, CheckUnits
 @public t, D, t_nounits, D_nounits, t_unitful, D_unitful
+@public SymbolicContinuousCallback, SymbolicDiscreteCallback
 
 for prop in [SYS_PROPS; [:continuous_events, :discrete_events]]
     getter = Symbol(:get_, prop)

From eb5f1fd9af427d961c26d27810d7162315ecc4f9 Mon Sep 17 00:00:00 2001
From: Aayush Sabharwal <aayush.sabharwal@gmail.com>
Date: Mon, 11 Aug 2025 06:45:13 +0530
Subject: [PATCH 05/12] refactor: mark `VariableType`, `MTKVariableTypeCtx` as
 public

---
 docs/src/API/variables.md |  9 +++++++++
 src/ModelingToolkit.jl    |  1 +
 src/parameters.jl         | 13 +++++++++++++
 3 files changed, 23 insertions(+)

diff --git a/docs/src/API/variables.md b/docs/src/API/variables.md
index 4c11d900c9..9724f3372b 100644
--- a/docs/src/API/variables.md
+++ b/docs/src/API/variables.md
@@ -263,6 +263,15 @@ hasunit
 getunit
 ```
 
+## Variable type
+
+This metadata is used by the [`System`](@ref) constructor for automatically identifying the different types of variables in a system.
+
+```@docs
+ModelingToolkit.VariableType
+ModelingToolkit.MTKVariableTypeCtx
+```
+
 ## Miscellaneous metadata
 
 User-defined metadata can be added using the `misc` metadata. This can be queried
diff --git a/src/ModelingToolkit.jl b/src/ModelingToolkit.jl
index 98a9267e57..4491b1a445 100644
--- a/src/ModelingToolkit.jl
+++ b/src/ModelingToolkit.jl
@@ -339,6 +339,7 @@ export DynamicOptSolution
 @public AbstractSystem, CheckAll, CheckNone, CheckComponents, CheckUnits
 @public t, D, t_nounits, D_nounits, t_unitful, D_unitful
 @public SymbolicContinuousCallback, SymbolicDiscreteCallback
+@public VariableType, MTKVariableTypeCtx
 
 for prop in [SYS_PROPS; [:continuous_events, :discrete_events]]
     getter = Symbol(:get_, prop)
diff --git a/src/parameters.jl b/src/parameters.jl
index de7a722af3..b53f7c6a76 100644
--- a/src/parameters.jl
+++ b/src/parameters.jl
@@ -1,5 +1,18 @@
 import SymbolicUtils: symtype, term, hasmetadata, issym
+
+"""
+    @enum VariableType
+
+The type of the declared variable, used for automatic identification of
+variables/parameters/brownians/etc. by the `System` constructor.
+"""
 @enum VariableType VARIABLE PARAMETER BROWNIAN
+
+"""
+    $TYPEDEF
+
+The symbolic metadata key for storing the `VariableType`.
+"""
 struct MTKVariableTypeCtx end
 
 getvariabletype(x, def = VARIABLE) = getmetadata(unwrap(x), MTKVariableTypeCtx, def)

From 91942a542b5c1f570cddfd663d1765f2b452188f Mon Sep 17 00:00:00 2001
From: Aayush Sabharwal <aayush.sabharwal@gmail.com>
Date: Mon, 11 Aug 2025 06:54:31 +0530
Subject: [PATCH 06/12] refactor: mark several variable metadata keys as public

---
 docs/src/API/variables.md |  9 ++++++++
 src/ModelingToolkit.jl    |  4 +++-
 src/variables.jl          | 46 +++++++++++++++++++++++++++++++++++++++
 3 files changed, 58 insertions(+), 1 deletion(-)

diff --git a/docs/src/API/variables.md b/docs/src/API/variables.md
index 9724f3372b..d5662f4f16 100644
--- a/docs/src/API/variables.md
+++ b/docs/src/API/variables.md
@@ -56,6 +56,7 @@ help?> u
 ```@docs
 hasdescription
 getdescription
+ModelingToolkit.VariableDescription
 ```
 
 ## Connect
@@ -83,6 +84,7 @@ getconnect(k)
 ```@docs
 hasconnect
 getconnect
+ModelingToolkit.VariableConnectType
 ```
 
 ```@docs; canonical=false
@@ -112,6 +114,8 @@ isinput
 isoutput
 ModelingToolkit.setinput
 ModelingToolkit.setoutput
+ModelingToolkit.VariableInput
+ModelingToolkit.VariableOutput
 ```
 
 ## Bounds
@@ -144,6 +148,7 @@ hasbounds(x[2])
 ```@docs
 hasbounds
 getbounds
+ModelingToolkit.VariableBounds
 ```
 
 ## Guess
@@ -232,6 +237,7 @@ isirreducible(important_value)
 
 ```@docs
 isirreducible
+ModelingToolkit.VariableIrreducible
 ```
 
 ## State Priority
@@ -245,6 +251,7 @@ state_priority(important_dof)
 
 ```@docs
 state_priority
+ModelingToolkit.VariableStatePriority
 ```
 
 ## Units
@@ -261,6 +268,7 @@ getunit(speed)
 ```@docs
 hasunit
 getunit
+ModelingToolkit.VariableUnit
 ```
 
 ## Variable type
@@ -286,6 +294,7 @@ getmisc(y)
 ```@docs
 hasmisc
 getmisc
+ModelingToolkit.VariableMisc
 ```
 
 ## Dumping metadata
diff --git a/src/ModelingToolkit.jl b/src/ModelingToolkit.jl
index 4491b1a445..a77b676ff0 100644
--- a/src/ModelingToolkit.jl
+++ b/src/ModelingToolkit.jl
@@ -339,7 +339,9 @@ export DynamicOptSolution
 @public AbstractSystem, CheckAll, CheckNone, CheckComponents, CheckUnits
 @public t, D, t_nounits, D_nounits, t_unitful, D_unitful
 @public SymbolicContinuousCallback, SymbolicDiscreteCallback
-@public VariableType, MTKVariableTypeCtx
+@public VariableType, MTKVariableTypeCtx, VariableBounds, VariableConnectType
+@public VariableDescription, VariableInput, VariableIrreducible, VariableMisc
+@public VariableOutput, VariableStatePriority, VariableUnit
 
 for prop in [SYS_PROPS; [:continuous_events, :discrete_events]]
     getter = Symbol(:get_, prop)
diff --git a/src/variables.jl b/src/variables.jl
index b61298eca2..051efd5853 100644
--- a/src/variables.jl
+++ b/src/variables.jl
@@ -1,10 +1,46 @@
+"""
+    $TYPEDEF
+
+Symbolic metadata key for storing the unit associated with a symbolic variable.
+"""
 struct VariableUnit end
+"""
+    $TYPEDEF
+
+Symbolic metadata key for storing the type of connector that a variable is.
+"""
 struct VariableConnectType end
 struct VariableNoiseType end
+"""
+    $TYPEDEF
+
+Symbolic metadata key for storing whether a symbolic variable is an input or not.
+"""
 struct VariableInput end
+"""
+    $TYPEDEF
+
+Symbolic metadata key for storing whether a symbolic variable is an output or not.
+"""
 struct VariableOutput end
+"""
+  $TYPEDEF
+
+Symbolic metadata key for storing whether a symbolic variable is irreducible or not.
+"""
 struct VariableIrreducible end
+"""
+    $TYPEDEF
+
+Symbolic metadata key for storing the priority a variable has for being selected during
+state selection.
+"""
 struct VariableStatePriority end
+"""
+    $TYPEDEF
+
+Symbolic metadata key for storing miscellaneous information about a symbolic variable.
+"""
 struct VariableMisc end
 # Metadata for renamed shift variables xₜ₋₁
 struct VariableUnshifted end
@@ -227,6 +263,11 @@ function default_toterm(x)
 end
 
 ## Bounds ======================================================================
+"""
+    $TYPEDEF
+
+Symbolic metadata key for specifying the bounds of a symbolic variable.
+"""
 struct VariableBounds end
 Symbolics.option_to_metadata_type(::Val{:bounds}) = VariableBounds
 
@@ -436,6 +477,11 @@ function getbounds(p::AbstractVector)
 end
 
 ## Description =================================================================
+"""
+    $TYPEDEF
+
+Symbolic metadata key for storing the description of a symbolic variable.
+"""
 struct VariableDescription end
 Symbolics.option_to_metadata_type(::Val{:description}) = VariableDescription
 

From e06c0294c7028440339c22cbcc331169ee07f3fb Mon Sep 17 00:00:00 2001
From: Aayush Sabharwal <aayush.sabharwal@gmail.com>
Date: Mon, 11 Aug 2025 07:50:11 +0530
Subject: [PATCH 07/12] refactor: remove `VariableNoiseType`

---
 src/systems/model_parsing.jl | 1 -
 src/variables.jl             | 1 -
 2 files changed, 2 deletions(-)

diff --git a/src/systems/model_parsing.jl b/src/systems/model_parsing.jl
index c24c063ee0..61edc394b2 100644
--- a/src/systems/model_parsing.jl
+++ b/src/systems/model_parsing.jl
@@ -186,7 +186,6 @@ function update_readable_metadata!(varclass_dict, meta::Dict, varname)
         (:description, VariableDescription),
         (:unit, VariableUnit),
         (:bounds, VariableBounds),
-        (:noise, VariableNoiseType),
         (:input, VariableInput),
         (:output, VariableOutput),
         (:irreducible, VariableIrreducible),
diff --git a/src/variables.jl b/src/variables.jl
index 051efd5853..46c9c95bc6 100644
--- a/src/variables.jl
+++ b/src/variables.jl
@@ -10,7 +10,6 @@ struct VariableUnit end
 Symbolic metadata key for storing the type of connector that a variable is.
 """
 struct VariableConnectType end
-struct VariableNoiseType end
 """
     $TYPEDEF
 

From 434b34aaf2377129dac1a270f58f95cbb8cedd6d Mon Sep 17 00:00:00 2001
From: Aayush Sabharwal <aayush.sabharwal@gmail.com>
Date: Mon, 11 Aug 2025 08:06:40 +0530
Subject: [PATCH 08/12] refactor: mark `collect_*` functions as public

---
 docs/src/API/System.md | 12 ++++++++++++
 src/ModelingToolkit.jl |  3 ++-
 2 files changed, 14 insertions(+), 1 deletion(-)

diff --git a/docs/src/API/System.md b/docs/src/API/System.md
index b5dd08bdc7..5160fa0b28 100644
--- a/docs/src/API/System.md
+++ b/docs/src/API/System.md
@@ -200,3 +200,15 @@ ModelingToolkit.CheckUnits
 ```
 
 These can also be used by custom `AbstractSystem` subtypes.
+
+## Utility functions
+
+These utility functions can be useful when manipulating systems, especially when building
+custom `AbstractSystem` subtypes.
+
+```@docs
+ModelingToolkit.collect_scoped_vars!
+ModelingToolkit.collect_var_to_name!
+ModelingToolkit.collect_vars!
+ModelingToolkit.eqtype_supports_collect_vars
+```
diff --git a/src/ModelingToolkit.jl b/src/ModelingToolkit.jl
index a77b676ff0..5abd639c37 100644
--- a/src/ModelingToolkit.jl
+++ b/src/ModelingToolkit.jl
@@ -341,7 +341,8 @@ export DynamicOptSolution
 @public SymbolicContinuousCallback, SymbolicDiscreteCallback
 @public VariableType, MTKVariableTypeCtx, VariableBounds, VariableConnectType
 @public VariableDescription, VariableInput, VariableIrreducible, VariableMisc
-@public VariableOutput, VariableStatePriority, VariableUnit
+@public VariableOutput, VariableStatePriority, VariableUnit, collect_scoped_vars!
+@public collect_var_to_name!, collect_vars!, eqtype_supports_collect_vars
 
 for prop in [SYS_PROPS; [:continuous_events, :discrete_events]]
     getter = Symbol(:get_, prop)

From 5c24fa12b6e2a18f2806ee1d80ea3db7f76b764f Mon Sep 17 00:00:00 2001
From: Aayush Sabharwal <aayush.sabharwal@gmail.com>
Date: Mon, 11 Aug 2025 08:22:55 +0530
Subject: [PATCH 09/12] refactor: mark variable default manipulation functions
 as public

---
 docs/src/API/variables.md | 11 +++++++++++
 src/ModelingToolkit.jl    |  3 ++-
 src/utils.jl              | 15 +++++++++++++++
 3 files changed, 28 insertions(+), 1 deletion(-)

diff --git a/docs/src/API/variables.md b/docs/src/API/variables.md
index d5662f4f16..7ccaa2999f 100644
--- a/docs/src/API/variables.md
+++ b/docs/src/API/variables.md
@@ -18,6 +18,17 @@ Symbolic variables can have metadata attached to them. The defaults and guesses
 at variable construction time are examples of this metadata. ModelingToolkit also defines
 additional types of metadata.
 
+## Variable defaults
+
+Variables can be assigned default values to avoid having to specify defaults to the
+[`System`](@ref) constructor.
+
+```@docs
+ModelingToolkit.hasdefault
+ModelingToolkit.getdefault
+ModelingToolkit.setdefault
+```
+
 ## Variable descriptions
 
 Descriptive strings can be attached to variables using the `[description = "descriptive string"]` syntax:
diff --git a/src/ModelingToolkit.jl b/src/ModelingToolkit.jl
index 5abd639c37..3ad8d3f0d9 100644
--- a/src/ModelingToolkit.jl
+++ b/src/ModelingToolkit.jl
@@ -342,7 +342,8 @@ export DynamicOptSolution
 @public VariableType, MTKVariableTypeCtx, VariableBounds, VariableConnectType
 @public VariableDescription, VariableInput, VariableIrreducible, VariableMisc
 @public VariableOutput, VariableStatePriority, VariableUnit, collect_scoped_vars!
-@public collect_var_to_name!, collect_vars!, eqtype_supports_collect_vars
+@public collect_var_to_name!, collect_vars!, eqtype_supports_collect_vars, hasdefault
+@public getdefault, setdefault
 
 for prop in [SYS_PROPS; [:continuous_events, :discrete_events]]
     getter = Symbol(:get_, prop)
diff --git a/src/utils.jl b/src/utils.jl
index 8ec9def5e9..c6f3777c2b 100644
--- a/src/utils.jl
+++ b/src/utils.jl
@@ -250,8 +250,23 @@ function iv_from_nested_derivative(x, op = Differential)
     end
 end
 
+"""
+    $(TYPEDSIGNATURES)
+
+Check if the symbolic variable `v` has a default value.
+"""
 hasdefault(v) = hasmetadata(v, Symbolics.VariableDefaultValue)
+"""
+    $(TYPEDSIGNATURES)
+
+Return the default value of symbolic variable `v`.
+"""
 getdefault(v) = value(Symbolics.getdefaultval(v))
+"""
+    $(TYPEDSIGNATURES)
+
+Set the default value of symbolic variable `v` to `val`.
+"""
 function setdefault(v, val)
     val === nothing ? v : wrap(setdefaultval(unwrap(v), value(val)))
 end

From 2c0aaa8e5154f8bbe871129b664bc9b27a420430 Mon Sep 17 00:00:00 2001
From: Aayush Sabharwal <aayush.sabharwal@gmail.com>
Date: Mon, 11 Aug 2025 08:26:29 +0530
Subject: [PATCH 10/12] refactor: mark `iscomplete`, `isparameter` as public

---
 docs/src/API/variables.md | 1 +
 src/ModelingToolkit.jl    | 2 +-
 src/parameters.jl         | 5 +++++
 3 files changed, 7 insertions(+), 1 deletion(-)

diff --git a/docs/src/API/variables.md b/docs/src/API/variables.md
index 7ccaa2999f..99fd53372c 100644
--- a/docs/src/API/variables.md
+++ b/docs/src/API/variables.md
@@ -289,6 +289,7 @@ This metadata is used by the [`System`](@ref) constructor for automatically iden
 ```@docs
 ModelingToolkit.VariableType
 ModelingToolkit.MTKVariableTypeCtx
+ModelingToolkit.isparameter
 ```
 
 ## Miscellaneous metadata
diff --git a/src/ModelingToolkit.jl b/src/ModelingToolkit.jl
index 3ad8d3f0d9..c12384ea0d 100644
--- a/src/ModelingToolkit.jl
+++ b/src/ModelingToolkit.jl
@@ -343,7 +343,7 @@ export DynamicOptSolution
 @public VariableDescription, VariableInput, VariableIrreducible, VariableMisc
 @public VariableOutput, VariableStatePriority, VariableUnit, collect_scoped_vars!
 @public collect_var_to_name!, collect_vars!, eqtype_supports_collect_vars, hasdefault
-@public getdefault, setdefault
+@public getdefault, setdefault, iscomplete, isparameter
 
 for prop in [SYS_PROPS; [:continuous_events, :discrete_events]]
     getter = Symbol(:get_, prop)
diff --git a/src/parameters.jl b/src/parameters.jl
index b53f7c6a76..7633d8c1b7 100644
--- a/src/parameters.jl
+++ b/src/parameters.jl
@@ -17,6 +17,11 @@ struct MTKVariableTypeCtx end
 
 getvariabletype(x, def = VARIABLE) = getmetadata(unwrap(x), MTKVariableTypeCtx, def)
 
+"""
+    $TYPEDEF
+
+Check if the variable contains the metadata identifying it as a parameter.
+"""
 function isparameter(x)
     x = unwrap(x)
 

From b002c9771831358d3692aed21aa5896f1bbe3e8f Mon Sep 17 00:00:00 2001
From: Aayush Sabharwal <aayush.sabharwal@gmail.com>
Date: Mon, 11 Aug 2025 09:08:26 +0530
Subject: [PATCH 11/12] refactor: mark `modified_unknowns!` as public

---
 docs/src/API/System.md      | 1 +
 src/ModelingToolkit.jl      | 2 +-
 src/problems/jumpproblem.jl | 7 +++++++
 3 files changed, 9 insertions(+), 1 deletion(-)

diff --git a/docs/src/API/System.md b/docs/src/API/System.md
index 5160fa0b28..34b64345d0 100644
--- a/docs/src/API/System.md
+++ b/docs/src/API/System.md
@@ -211,4 +211,5 @@ ModelingToolkit.collect_scoped_vars!
 ModelingToolkit.collect_var_to_name!
 ModelingToolkit.collect_vars!
 ModelingToolkit.eqtype_supports_collect_vars
+ModelingToolkit.modified_unknowns!
 ```
diff --git a/src/ModelingToolkit.jl b/src/ModelingToolkit.jl
index c12384ea0d..4057d48921 100644
--- a/src/ModelingToolkit.jl
+++ b/src/ModelingToolkit.jl
@@ -343,7 +343,7 @@ export DynamicOptSolution
 @public VariableDescription, VariableInput, VariableIrreducible, VariableMisc
 @public VariableOutput, VariableStatePriority, VariableUnit, collect_scoped_vars!
 @public collect_var_to_name!, collect_vars!, eqtype_supports_collect_vars, hasdefault
-@public getdefault, setdefault, iscomplete, isparameter
+@public getdefault, setdefault, iscomplete, isparameter, modified_unknowns!
 
 for prop in [SYS_PROPS; [:continuous_events, :discrete_events]]
     getter = Symbol(:get_, prop)
diff --git a/src/problems/jumpproblem.jl b/src/problems/jumpproblem.jl
index 3bc0e11f61..32aa25182f 100644
--- a/src/problems/jumpproblem.jl
+++ b/src/problems/jumpproblem.jl
@@ -210,6 +210,13 @@ function get_variables!(dep, jump::MassActionJump, variables)
 end
 
 ### Functions to determine which unknowns are modified by a given jump
+
+"""
+    $(TYPEDSIGNATURES)
+
+Push to `munknowns` the variables modified by jump `jump`. `sts` is the list of unknowns of
+the system. Return the modified `munknowns`.
+"""
 function modified_unknowns!(munknowns, jump::Union{ConstantRateJump, VariableRateJump}, sts)
     for eq in jump.affect!
         st = eq.lhs

From ba7ee6004f16b84bc82a89f20652ca995c6c9bf7 Mon Sep 17 00:00:00 2001
From: Aayush Sabharwal <aayush.sabharwal@gmail.com>
Date: Mon, 11 Aug 2025 09:13:16 +0530
Subject: [PATCH 12/12] refactor: mark `renamespace`, `namespace_equations` as
 public

---
 docs/src/API/System.md        | 11 +++++++++++
 src/ModelingToolkit.jl        |  1 +
 src/systems/abstractsystem.jl | 16 ++++++++++++++++
 3 files changed, 28 insertions(+)

diff --git a/docs/src/API/System.md b/docs/src/API/System.md
index 34b64345d0..c7cf3cdd9b 100644
--- a/docs/src/API/System.md
+++ b/docs/src/API/System.md
@@ -213,3 +213,14 @@ ModelingToolkit.collect_vars!
 ModelingToolkit.eqtype_supports_collect_vars
 ModelingToolkit.modified_unknowns!
 ```
+
+## Namepsace manipulation
+
+ModelingToolkit namespaces variables from subsystems when using them in a parent system to
+disambiguate from identically named variables in other subsystems or the parent system. The
+following functions are useful for manipulating namespacing functionality.
+
+```@docs
+ModelingToolkit.renamespace
+ModelingToolkit.namespace_equations
+```
diff --git a/src/ModelingToolkit.jl b/src/ModelingToolkit.jl
index 4057d48921..26efc0c7a9 100644
--- a/src/ModelingToolkit.jl
+++ b/src/ModelingToolkit.jl
@@ -344,6 +344,7 @@ export DynamicOptSolution
 @public VariableOutput, VariableStatePriority, VariableUnit, collect_scoped_vars!
 @public collect_var_to_name!, collect_vars!, eqtype_supports_collect_vars, hasdefault
 @public getdefault, setdefault, iscomplete, isparameter, modified_unknowns!
+@public renamespace, namespace_equations
 
 for prop in [SYS_PROPS; [:continuous_events, :discrete_events]]
     getter = Symbol(:get_, prop)
diff --git a/src/systems/abstractsystem.jl b/src/systems/abstractsystem.jl
index 3fe04936d3..f9d9a196b4 100644
--- a/src/systems/abstractsystem.jl
+++ b/src/systems/abstractsystem.jl
@@ -1095,6 +1095,12 @@ end
 renamespace(sys, eq::Equation) = namespace_equation(eq, sys)
 
 renamespace(names::AbstractVector, x) = foldr(renamespace, names, init = x)
+
+"""
+    $(TYPEDSIGNATURES)
+
+Namespace `x` with the name of `sys`.
+"""
 function renamespace(sys, x)
     sys === nothing && return x
     x = unwrap(x)
@@ -1141,6 +1147,11 @@ function namespace_guesses(sys)
     Dict(unknowns(sys, k) => namespace_expr(v, sys) for (k, v) in guess)
 end
 
+"""
+    $(TYPEDSIGNATURES)
+
+Return `equations(sys)`, namespaced by the name of `sys`.
+"""
 function namespace_equations(sys::AbstractSystem, ivs = independent_variables(sys))
     eqs = equations(sys)
     isempty(eqs) && return Equation[]
@@ -1162,6 +1173,11 @@ function namespace_tstops(sys::AbstractSystem)
     end
 end
 
+"""
+    $(TYPEDSIGNATURES)
+
+Namespace the given equation with the name of the given system `sys`.
+"""
 function namespace_equation(eq::Equation,
         sys,
         n = nameof(sys);