diff --git a/elm.json b/elm.json
index cf63307..fb3de0a 100644
--- a/elm.json
+++ b/elm.json
@@ -23,6 +23,7 @@
         "Internal.Values.Event",
         "Internal.Values.Settings",
         "Internal.Values.StateManager",
+        "Internal.Values.Timeline",
         "Internal.Values.Vault",
         "Matrix",
         "Matrix.Event",
diff --git a/src/Internal/Config/Text.elm b/src/Internal/Config/Text.elm
index df063b5..76c8bd6 100644
--- a/src/Internal/Config/Text.elm
+++ b/src/Internal/Config/Text.elm
@@ -1,5 +1,5 @@
 module Internal.Config.Text exposing
-    ( docs, failures, fields
+    ( docs, failures, fields, mappings
     , accessTokenFoundLocally, accessTokenExpired, accessTokenInvalid
     , versionsFoundLocally, versionsReceived, versionsFailedToDecode
     , unsupportedVersionForEndpoint
@@ -27,7 +27,7 @@ You should only do this if you know what you're doing.
 
 ## Type documentation
 
-@docs docs, failures, fields
+@docs docs, failures, fields, mappings
 
 
 ## API Authentication
@@ -347,6 +347,19 @@ leakingValueFound leaking_value =
     "Found leaking value : " ++ leaking_value
 
 
+{-| Function descriptions
+-}
+mappings : { itokenPTR : TypeDocs }
+mappings =
+    { itokenPTR =
+        { name = "ITokenPTR init"
+        , description =
+            [ "Converts an optional string to an Itoken pointer."
+            ]
+        }
+    }
+
+
 {-| The Matrix homeserver can specify how it wishes to communicate, and the Elm
 SDK aims to communicate accordingly. This may fail in some scenarios, however,
 in which case it will throw this error.
diff --git a/src/Internal/Tools/Json.elm b/src/Internal/Tools/Json.elm
index 1a9ca12..44ab34c 100644
--- a/src/Internal/Tools/Json.elm
+++ b/src/Internal/Tools/Json.elm
@@ -3,7 +3,7 @@ module Internal.Tools.Json exposing
     , Encoder, encode, Decoder, decode, Value
     , succeed, fail, andThen, lazy, map
     , Docs(..), RequiredField(..), toDocs
-    , list, slowDict, fastDict, maybe
+    , list, slowDict, fastDict, set, maybe
     , Field, field
     , object2, object3, object4, object5, object6, object7, object8, object9, object10, object11
     )
@@ -49,7 +49,7 @@ module to build its encoders and decoders.
 
 ## Data types
 
-@docs list, slowDict, fastDict, maybe
+@docs list, slowDict, fastDict, set, maybe
 
 
 ## Objects
@@ -73,6 +73,7 @@ import Internal.Tools.DecodeExtra as D
 import Internal.Tools.EncodeExtra as E
 import Json.Decode as D
 import Json.Encode as E
+import Set exposing (Set)
 
 
 {-| A field of type `a` as a subtype of an object `object`.
@@ -155,6 +156,7 @@ type Docs
         )
     | DocsOptional Docs
     | DocsRiskyMap (Descriptive { content : Docs, failure : List String })
+    | DocsSet Docs
     | DocsString
     | DocsValue
 
@@ -1079,6 +1081,27 @@ object11 { name, description, init } fa fb fc fd fe ff fg fh fi fj fk =
         }
 
 
+{-| Define a set.
+-}
+set : Coder comparable -> Coder (Set comparable)
+set (Coder data) =
+    Coder
+        { encoder = E.set data.encoder
+        , decoder =
+            data.decoder
+                |> D.list
+                |> D.map
+                    (\items ->
+                        ( items
+                            |> List.map Tuple.first
+                            |> Set.fromList
+                        , items
+                            |> List.concatMap Tuple.second
+                        )
+                    )
+        , docs = DocsSet data.docs
+        }
+
 {-| Define a slow dict from the `elm/core` library.
 -}
 slowDict : Coder value -> Coder (SlowDict.Dict String value)
diff --git a/src/Internal/Values/Timeline.elm b/src/Internal/Values/Timeline.elm
index 305e2a0..2ad3e8d 100644
--- a/src/Internal/Values/Timeline.elm
+++ b/src/Internal/Values/Timeline.elm
@@ -61,7 +61,7 @@ events!
 
 ## JSON coder
 
-@docs encode, decoder
+@docs coder, encode, decoder
 
 -}
 
@@ -70,6 +70,7 @@ import Internal.Filter.Timeline as Filter exposing (Filter)
 import Internal.Tools.Hashdict as Hashdict exposing (Hashdict)
 import Internal.Tools.Iddict as Iddict exposing (Iddict)
 import Internal.Tools.Json as Json
+import Internal.Config.Text as Text
 import Json.Decode as D
 import Json.Encode as E
 import Recursion
@@ -79,6 +80,9 @@ import Set exposing (Set)
 
 {-| A batch is a batch of events that is placed onto the Timeline. Functions
 that require an insertion, generally require this data type.
+
+If the `start` value is `Nothing`, it is either the start of the timeline or the
+start of the timeline part that the user is allowed to view.
 -}
 type alias Batch =
     { events : List String
@@ -164,6 +168,83 @@ type Timeline
 type alias TokenValue =
     String
 
+coderIBatchPTR : Json.Coder IBatchPTR
+coderIBatchPTR =
+    Json.map
+        { name = Debug.todo "Add name"
+        , description = Debug.todo "Add description"
+        , back = IBatchPTR
+        , forth = (\(IBatchPTR value) -> value)
+        }
+        coderIBatchPTRValue
+
+coderIBatchPTRValue : Json.Coder IBatchPTRValue
+coderIBatchPTRValue = Json.int
+
+coderIToken : Json.Coder IToken
+coderIToken =
+    Json.object5
+        { name = "IToken"
+        , description = Debug.todo "TODO: Add description"
+        , init = IToken
+        }
+        ( Json.field.required
+            { fieldName = "name"
+            , toField = .name
+            , description = Debug.todo "TODO: Add description"
+            , coder = coderTokenValue
+            }
+        )
+        ( Json.field.optional.withDefault
+            { fieldName = "starts"
+            , toField = .starts
+            , description = Debug.todo "TODO: Add description"
+            , coder = Json.set coderIBatchPTRValue
+            , default = ( Set.empty, [] )
+            , defaultToString = always "[]"
+            }
+        )
+        ( Json.field.optional.withDefault
+            { fieldName = "ends"
+            , toField = .ends
+            , description = Debug.todo "TODO: Add description"
+            , coder = Json.set coderIBatchPTRValue
+            , default = ( Set.empty, [] )
+            , defaultToString = always "[]"
+            }
+        )
+
+coderITokenPTR : Json.Coder ITokenPTR
+coderITokenPTR =
+    Json.maybe coderITokenPTRValue
+        |> Json.map
+            { name = Text.mappings.itokenPTR.name
+            , description = Text.mappings.itokenPTR.description
+            , back =
+                (\itokenptr ->
+                    case itokenptr of
+                        ITokenPTR name ->
+                            Just name
+                        
+                        StartOfTimeline ->
+                            Nothing
+                )
+            , forth =
+                (\value ->
+                    case value of
+                        Just name ->
+                            ITokenPTR name
+                        
+                        Nothing ->
+                            StartOfTimeline
+                )
+            }
+
+coderITokenPTRValue : Json.Coder ITokenPTRValue
+coderITokenPTRValue = Json.string
+
+coderTokenValue : Json.Coder TokenValue
+coderTokenValue = Json.string
 
 {-| Append a token at the end of a batch.
 -}
diff --git a/tests/Test/Values/Timeline.elm b/tests/Test/Values/Timeline.elm
index c2e3a96..3bca09d 100644
--- a/tests/Test/Values/Timeline.elm
+++ b/tests/Test/Values/Timeline.elm
@@ -170,7 +170,7 @@ suite =
             ]
         , describe "Gaps"
             [ fuzz TestFilter.fuzzer
-                "Gap leaves behind old events"
+                "Gaps leave behind old events"
                 (\filter ->
                     Timeline.empty
                         |> Timeline.insert
@@ -189,7 +189,7 @@ suite =
                         |> Expect.equal [ [ "d", "e", "f" ] ]
                 )
             , fuzz TestFilter.fuzzer
-                "Gap can be bridged"
+                "Gaps can be bridged"
                 (\filter ->
                     Timeline.empty
                         |> Timeline.insert