Name the tokenizer a model uses, where its vendor does

app/MindWork AI Studio/Dialogs/ProviderDialog.razor

@@ -251,6 +251,13 @@
                         <MudJustifiedText Typo="Typo.body1" Class="mt-4 mb-3">
                             @T("For better token estimates, you can configure a custom tokenizer for this provider.")
                         </MudJustifiedText>
+                        var tokenizerHint = this.GetCurrentModelTokenizerLabel();
+                        if (!string.IsNullOrEmpty(tokenizerHint))
+                        {
+                            <MudJustifiedText Typo="Typo.body2" Class="mb-3">
+                                @tokenizerHint
+                            </MudJustifiedText>
+                        }
                         <PathDropZone IdPrefix="tokenizer" Disabled="@(() => this.IsEnterpriseConfiguration)" OnPathsDropped="@this.OnTokenizerPathsDropped">
                             <MudStack Row="@true" Spacing="3" Class="mb-3" StretchItems="StretchItems.None" AlignItems="AlignItems.Center">
                                 <MudTextField

app/MindWork AI Studio/Dialogs/ProviderDialog.razor.cs

@@ -778,6 +778,35 @@ public partial class ProviderDialog : MSGComponentBase, ISecretId
         return "Unknown";
     }
 
+    /// <summary>
+    /// What the dialog says about the tokenizer of the current model, if anything.
+    /// </summary>
+    /// <remarks>
+    /// The field below this sentence takes a tokenizer.json file and nothing else, and until now it
+    /// said nothing about which file. That leaves two kinds of people stuck: the ones who could
+    /// download the right file and do not know its name, and the ones who spend an evening looking
+    /// for Anthropic's tokenizer file, which does not exist.
+    ///
+    /// Empty for a model nobody stated a tokenizer for, which is most of them. An empty sentence
+    /// hides the whole line rather than claiming that nothing is known about it.
+    /// </remarks>
+    /// <returns>The sentence, or nothing.</returns>
+    private string GetCurrentModelTokenizerLabel()
+    {
+        var tokenizer = this.GetCurrentModelProfile().Tokenizer;
+        if (!tokenizer.IsKnown)
+            return string.Empty;
+
+        return tokenizer.Kind switch
+        {
+            TokenizerKind.HUGGING_FACE => string.Format(T("This model uses the tokenizer of {0}. Download its tokenizer.json file and select it below to count exactly instead of estimating."), tokenizer.Id),
+            TokenizerKind.TIKTOKEN => string.Format(T("This model uses OpenAI's {0} encoding, which does not come as a tokenizer.json file. AI Studio therefore estimates the token count with its built-in tokenizer."), tokenizer.Id),
+            TokenizerKind.PROVIDER_API => string.Format(T("The vendor of this model publishes no tokenizer file and counts through their API instead ({0}). AI Studio therefore estimates the token count with its built-in tokenizer."), tokenizer.Id),
+
+            _ => string.Empty,
+        };
+    }
+
     private string GetCapabilityOverrideLabel(Capability capability) => capability switch
     {
         Capability.AUDIO_INPUT => T("Audio input"),