diff --git a/Build/Publish-Module.ps1 b/Build/Publish-Module.ps1
index 00618f0..d018f2a 100644
--- a/Build/Publish-Module.ps1
+++ b/Build/Publish-Module.ps1
@@ -185,6 +185,22 @@ if (-not $WhatIfPreference -and -not $ApiKey) {
     }
 }
 
+# The tags the Gallery lists for a published module: the manifest's, then the ones the publish
+# adds for the package kind, the editions and every exported function.
+function Get-PublishedTag {
+    param([Parameter(Mandatory)]$Manifest)
+    $tags = [System.Collections.Generic.List[string]]::new()
+    foreach ($tag in @($Manifest.Tags)) { $tags.Add($tag) }
+    $tags.Add('PSModule')
+    foreach ($edition in @($Manifest.CompatiblePSEditions)) { $tags.Add("PSEdition_$edition") }
+    foreach ($name in @($Manifest.ExportedFunctions.Keys | Sort-Object)) {
+        $tags.Add("PSFunction_$name")
+        $tags.Add("PSCommand_$name")
+    }
+    if ($Manifest.ExportedFunctions.Count) { $tags.Add('PSIncludes_Function') }
+    $tags
+}
+
 # --- 1. Help gates ----------------------------------------------------------------
 # Before staging, because a stale-MAML failure should stop the release rather than leave a
 # staged tree that nobody notices is wrong.
@@ -236,6 +252,32 @@ if ($releaseNotesLength -gt $releaseNotesLimit) {
         "$releaseNotesLimit. Move the older versions out, CHANGELOG.md has them.")
 }
 
+# NuGet's limit on a package description, which the Gallery applies.
+$descriptionLimit = 4000
+$descriptionLength = "$($manifest.Description)".Length
+if ($descriptionLength -gt $descriptionLimit) {
+    throw ("The manifest's Description is $descriptionLength characters; the Gallery accepts at most " +
+        "$descriptionLimit.")
+}
+
+# The Gallery refuses a package whose tags pass 4,000 characters ("A nuget package's Tags property
+# may not be more than 4000 characters long"), and the tags it measures are not the manifest's
+# alone: the publish adds PSModule, one PSEdition_ tag per compatible edition, PSFunction_ and
+# PSCommand_ for every exported function, and PSIncludes_Function. That is the list the Gallery
+# shows for 0.27.0 (61 tags, 1,935 characters for 27 commands), so every new command costs about
+# twice its name. Measured here the way the Gallery sees it.
+$tagsLimit = 4000
+$publishedTags = Get-PublishedTag -Manifest $manifest
+$tagsLength = ($publishedTags -join ' ').Length
+if ($tagsLength -gt $tagsLimit) {
+    throw ("The package's tags come to $tagsLength characters once the publish adds its own for " +
+        "$($manifest.ExportedFunctions.Count) commands; the Gallery accepts at most $tagsLimit. Drop " +
+        'manifest tags, or fewer commands.')
+}
+$metadataSummary = ("Gallery metadata: Description $descriptionLength/$descriptionLimit, Tags " +
+    "$tagsLength/$tagsLimit, ReleaseNotes $releaseNotesLength/$releaseNotesLimit characters.")
+Write-Information $metadataSummary -InformationAction Continue
+
 # --- 3. Already published? --------------------------------------------------------
 # A version number is consumed forever on first publish. Learning that from a rejected
 # upload is worse than a check costing one request.
diff --git a/CHANGELOG.md b/CHANGELOG.md
index a837347..9c39608 100644
--- a/CHANGELOG.md
+++ b/CHANGELOG.md
@@ -52,6 +52,11 @@ release notes.
   `Import-Clixml`, a cast or a `[pscredential]` parameter, the finding is a note that says the call can go.
   A variable with any other source, a member or a call stays a warning.
 
+- The release rehearsal (`Build/Publish-Module.ps1 -WhatIf`) measures the manifest's `Description` and the
+  package's tags against the Gallery's 4,000-character limits, next to the `ReleaseNotes` check from 0.27.0.
+  The tags counted are the ones the Gallery lists, the manifest's plus `PSModule`, the editions and two per
+  exported command, so a new command costs about twice its name. The module contract test holds the same
+  three limits, so a pull request fails before a release does.
 ## [0.27.0] - 2026-10-05
 
 Fixes to the runtime harness and to four rules, each rule change backed by a tenth validation
diff --git a/Tests/Unit/Module.Contract.Tests.ps1 b/Tests/Unit/Module.Contract.Tests.ps1
index b5db9b1..17c345d 100644
--- a/Tests/Unit/Module.Contract.Tests.ps1
+++ b/Tests/Unit/Module.Contract.Tests.ps1
@@ -26,6 +26,33 @@ Describe 'IntuneScriptLab module contract' -Tag 'Unit', 'Contract' {
         @((Test-ModuleManifest -Path $script:ManifestPath).RequiredModules).Count | Should-Be 0
     }
 
+    It 'keeps the Gallery metadata within the limits the Gallery enforces: <Field>' -ForEach @(
+        @{ Field = 'ReleaseNotes'; Limit = 10600 }
+        @{ Field = 'Description'; Limit = 4000 }
+        @{ Field = 'Tags'; Limit = 4000 }
+    ) {
+        # The Gallery refused 0.27.0's first upload: "A package's ReleaseNotes property extracted from
+        # the PowerShell manifest may not be more than 10600 characters long". Description and Tags
+        # carry NuGet's 4,000. The tags it measures include the ones the publish adds, PSModule, a
+        # PSEdition_ tag per edition, PSFunction_ and PSCommand_ per exported function and
+        # PSIncludes_Function: the list the Gallery shows for 0.27.0. Build/Publish-Module.ps1 checks
+        # the same three; this fails the pull request instead of the tag-driven release.
+        $manifest = Test-ModuleManifest -Path $script:ManifestPath
+        $text = switch ($Field) {
+            'ReleaseNotes' { "$($manifest.ReleaseNotes)" }
+            'Description' { "$($manifest.Description)" }
+            'Tags' {
+                $tags = @($manifest.Tags) + 'PSModule'
+                $tags += @($manifest.CompatiblePSEditions | ForEach-Object { "PSEdition_$_" })
+                foreach ($name in @($manifest.ExportedFunctions.Keys | Sort-Object)) {
+                    $tags += "PSFunction_$name", "PSCommand_$name"
+                }
+                ($tags + 'PSIncludes_Function') -join ' '
+            }
+        }
+        $text.Length | Should-BeLessThanOrEqual $Limit
+    }
+
     It 'exports exactly the public functions' {
         $exported = @((Get-Command -Module IntuneScriptLab -CommandType Function).Name | Sort-Object)
         $exported | Should-BeCollection @(