diff --git a/plugins/clarity-assist/hooks/hooks.json b/plugins/clarity-assist/hooks/hooks.json
new file mode 100644
index 0000000..65cf6a3
--- /dev/null
+++ b/plugins/clarity-assist/hooks/hooks.json
@@ -0,0 +1,10 @@
+{
+  "hooks": {
+    "UserPromptSubmit": [
+      {
+        "type": "command",
+        "command": "${CLAUDE_PLUGIN_ROOT}/hooks/vagueness-check.sh"
+      }
+    ]
+  }
+}
diff --git a/plugins/clarity-assist/hooks/vagueness-check.sh b/plugins/clarity-assist/hooks/vagueness-check.sh
new file mode 100755
index 0000000..4efaac1
--- /dev/null
+++ b/plugins/clarity-assist/hooks/vagueness-check.sh
@@ -0,0 +1,216 @@
+#!/bin/bash
+# clarity-assist vagueness detection hook
+# Analyzes user prompts for vagueness and suggests /clarity-assist when beneficial
+# All output MUST have [clarity-assist] prefix
+# This is a NON-BLOCKING hook - always exits 0
+
+PREFIX="[clarity-assist]"
+
+# Check if auto-suggest is enabled (default: true)
+AUTO_SUGGEST="${CLARITY_ASSIST_AUTO_SUGGEST:-true}"
+if [[ "$AUTO_SUGGEST" != "true" ]]; then
+    exit 0
+fi
+
+# Threshold for vagueness score (default: 0.6)
+THRESHOLD="${CLARITY_ASSIST_VAGUENESS_THRESHOLD:-0.6}"
+
+# Read user prompt from stdin
+PROMPT=""
+if [[ -t 0 ]]; then
+    # No stdin available
+    exit 0
+else
+    PROMPT=$(cat)
+fi
+
+# Skip empty prompts
+if [[ -z "$PROMPT" ]]; then
+    exit 0
+fi
+
+# Skip if prompt is a command (starts with /)
+if [[ "$PROMPT" =~ ^[[:space:]]*/[a-zA-Z] ]]; then
+    exit 0
+fi
+
+# Skip if prompt mentions specific files or paths
+if [[ "$PROMPT" =~ \.(py|js|ts|sh|md|json|yaml|yml|txt|css|html|go|rs|java|c|cpp|h)([[:space:]]|$|[^a-zA-Z]) ]] || \
+   [[ "$PROMPT" =~ [/\\][a-zA-Z0-9_-]+[/\\] ]] || \
+   [[ "$PROMPT" =~ (src|lib|test|docs|plugins|hooks|commands)/ ]]; then
+    exit 0
+fi
+
+# Initialize vagueness score
+SCORE=0
+
+# Count words in the prompt
+WORD_COUNT=$(echo "$PROMPT" | wc -w | tr -d ' ')
+
+# ============================================================================
+# Vagueness Signal Detection
+# ============================================================================
+
+# Signal 1: Very short prompts (< 10 words) are often vague
+if [[ "$WORD_COUNT" -lt 10 ]]; then
+    # But very short specific commands are OK
+    if [[ "$WORD_COUNT" -lt 3 ]]; then
+        # Extremely short - probably intentional or a command
+        :
+    else
+        SCORE=$(echo "$SCORE + 0.3" | bc)
+    fi
+fi
+
+# Signal 2: Vague action phrases (no specific outcome)
+VAGUE_ACTIONS=(
+    "help me"
+    "help with"
+    "do something"
+    "work on"
+    "look at"
+    "check this"
+    "fix it"
+    "fix this"
+    "make it better"
+    "make this better"
+    "improve it"
+    "improve this"
+    "update this"
+    "update it"
+    "change it"
+    "change this"
+    "can you"
+    "could you"
+    "would you"
+    "please help"
+)
+
+PROMPT_LOWER=$(echo "$PROMPT" | tr '[:upper:]' '[:lower:]')
+
+for phrase in "${VAGUE_ACTIONS[@]}"; do
+    if [[ "$PROMPT_LOWER" == *"$phrase"* ]]; then
+        SCORE=$(echo "$SCORE + 0.2" | bc)
+        break
+    fi
+done
+
+# Signal 3: Ambiguous scope indicators
+AMBIGUOUS_SCOPE=(
+    "somehow"
+    "something"
+    "somewhere"
+    "anything"
+    "whatever"
+    "stuff"
+    "things"
+    "etc"
+    "and so on"
+)
+
+for word in "${AMBIGUOUS_SCOPE[@]}"; do
+    if [[ "$PROMPT_LOWER" == *"$word"* ]]; then
+        SCORE=$(echo "$SCORE + 0.15" | bc)
+        break
+    fi
+done
+
+# Signal 4: Missing context indicators (no reference to what/where)
+# Check if prompt lacks specificity markers
+HAS_SPECIFICS=false
+
+# Specific technical terms suggest clarity
+SPECIFIC_MARKERS=(
+    "function"
+    "class"
+    "method"
+    "variable"
+    "error"
+    "bug"
+    "test"
+    "api"
+    "endpoint"
+    "database"
+    "query"
+    "component"
+    "module"
+    "service"
+    "config"
+    "install"
+    "deploy"
+    "build"
+    "run"
+    "execute"
+    "create"
+    "delete"
+    "add"
+    "remove"
+    "implement"
+    "refactor"
+    "migrate"
+    "upgrade"
+    "debug"
+    "log"
+    "exception"
+    "stack"
+    "memory"
+    "performance"
+    "security"
+    "auth"
+    "token"
+    "session"
+    "route"
+    "controller"
+    "model"
+    "view"
+    "template"
+    "schema"
+    "migration"
+    "commit"
+    "branch"
+    "merge"
+    "pull"
+    "push"
+)
+
+for marker in "${SPECIFIC_MARKERS[@]}"; do
+    if [[ "$PROMPT_LOWER" == *"$marker"* ]]; then
+        HAS_SPECIFICS=true
+        break
+    fi
+done
+
+if [[ "$HAS_SPECIFICS" == false ]] && [[ "$WORD_COUNT" -gt 3 ]]; then
+    SCORE=$(echo "$SCORE + 0.2" | bc)
+fi
+
+# Signal 5: Question without context
+if [[ "$PROMPT" =~ \?$ ]] && [[ "$WORD_COUNT" -lt 8 ]]; then
+    # Short questions without specifics are often vague
+    if [[ "$HAS_SPECIFICS" == false ]]; then
+        SCORE=$(echo "$SCORE + 0.15" | bc)
+    fi
+fi
+
+# Cap score at 1.0
+if (( $(echo "$SCORE > 1.0" | bc -l) )); then
+    SCORE="1.0"
+fi
+
+# ============================================================================
+# Output suggestion if score exceeds threshold
+# ============================================================================
+
+# Compare score to threshold using bc
+if (( $(echo "$SCORE >= $THRESHOLD" | bc -l) )); then
+    # Format score as percentage for display
+    SCORE_PCT=$(echo "$SCORE * 100" | bc | cut -d'.' -f1)
+
+    # Gentle, non-blocking suggestion
+    echo "$PREFIX Your prompt could benefit from more clarity."
+    echo "$PREFIX Consider running /clarity-assist to refine your request."
+    echo "$PREFIX (Vagueness score: ${SCORE_PCT}% - this is a suggestion, not a block)"
+fi
+
+# Always exit 0 - this hook is non-blocking
+exit 0