diff --git a/handlers/ssh_config/analyzer/analyzer.go b/handlers/ssh_config/analyzer/analyzer.go
index 83a230a..74d54b1 100644
--- a/handlers/ssh_config/analyzer/analyzer.go
+++ b/handlers/ssh_config/analyzer/analyzer.go
@@ -41,6 +41,7 @@ func Analyze(
 	analyzeBlocks(ctx)
 	analyzeMatchBlocks(ctx)
 	analyzeHostBlock(ctx)
+	analyzeBlocks(ctx)
 
 	return ctx.diagnostics
 }
diff --git a/handlers/ssh_config/analyzer/tag.go b/handlers/ssh_config/analyzer/tag.go
new file mode 100644
index 0000000..4208d31
--- /dev/null
+++ b/handlers/ssh_config/analyzer/tag.go
@@ -0,0 +1,28 @@
+package analyzer
+
+import (
+	"config-lsp/common"
+	"config-lsp/handlers/ssh_config/fields"
+	"fmt"
+
+	protocol "github.com/tliron/glsp/protocol_3_16"
+)
+
+var tagOption = fields.CreateNormalizedName("Tag")
+
+func analyzeTags(
+	ctx *analyzerContext,
+) {
+	// Check if the specified tags actually exist
+	for _, options := range ctx.document.Indexes.AllOptionsPerName[tagOption] {
+		for _, option := range options {
+			if _, found := ctx.document.Indexes.Tags[option.OptionValue.Value.Value]; !found {
+				ctx.diagnostics = append(ctx.diagnostics, protocol.Diagnostic{
+					Range:    option.OptionValue.ToLSPRange(),
+					Message:  fmt.Sprintf("Unknown tag: %s", option.OptionValue.Value.Value),
+					Severity: &common.SeverityError,
+				})
+			}
+		}
+	}
+}
diff --git a/handlers/ssh_config/fields/fields.go b/handlers/ssh_config/fields/fields.go
index 1906f6d..59caccf 100644
--- a/handlers/ssh_config/fields/fields.go
+++ b/handlers/ssh_config/fields/fields.go
@@ -905,7 +905,6 @@ rsa-sha2-512,rsa-sha2-256
     To disable TCP keepalive messages, the value should be set to no. See also ServerAliveInterval for protocol-level keepalives.`,
 		Value: booleanEnumValue,
 	},
-	// TODO: Add
 	"tag": {
 		Documentation: `Specify a configuration tag name that may be later used by a Match directive to select a block of configuration.`,
 		Value:         docvalues.StringValue{},