diff --git a/.github/workflows/test.yml b/.github/workflows/test.yml
index eb369e1..b686534 100644
--- a/.github/workflows/test.yml
+++ b/.github/workflows/test.yml
@@ -1,8 +1,9 @@
 name: test
-on: [push, pull_request]
+on: pull_request
 
 permissions:
   contents: read
+  pull-requests: write
 
 jobs:
   test:
@@ -18,7 +19,9 @@ jobs:
       - name: Run action
         uses: ./
 
-      - name: Run action with version
+      - name: Run action with inputs
         uses: ./
         with:
-          version: 2.3.4
+          model: codellama
+          prompt: 'Summarize code diff in bullet points:'
+          token: ${{ github.token }}
diff --git a/README.md b/README.md
index ae32e83..18cc414 100644
--- a/README.md
+++ b/README.md
@@ -24,7 +24,7 @@ jobs:
 
 ## Usage
 
-**Basic:**
+Append summary to PR description:
 
 ```yaml
 - uses: ai-action/pull-request-summary@v1
@@ -34,14 +34,34 @@ See [action.yml](action.yml)
 
 ## Inputs
 
-### `version`
+### `model`
 
-**Optional**: The version. Defaults to `1.2.3`:
+**Optional**: The language [model](https://ollama.com/library) to use. Defaults to [codellama](https://ollama.com/library/codellama):
 
 ```yaml
 - uses: ai-action/pull-request-summary@v1
   with:
-    version: 1.2.3
+    model: codellama
+```
+
+### `prompt`
+
+**Optional**: The input prompt that comes before the PR diff. Defaults to:
+
+```yaml
+- uses: ai-action/pull-request-summary@v1
+  with:
+    prompt: 'Summarize the code diff concisely:'
+```
+
+### `token`
+
+**Optional**: The GitHub token. Defaults to `GITHUB_TOKEN`:
+
+```yaml
+- uses: ai-action/pull-request-summary@v1
+  with:
+    token: ${{ secrets.GITHUB_TOKEN }}
 ```
 
 ## License
diff --git a/action.yml b/action.yml
index c5401b0..4d080b1 100644
--- a/action.yml
+++ b/action.yml
@@ -1,20 +1,51 @@
 name: pull-request-summary
-description: GitHub Action that reviews pull requests with AI (LLM)
+description: GitHub Action that summarizes pull requests with AI (LLM)
 author: remarkablemark
 
 inputs:
-  version:
-    description: Description
+  model:
+    description: Language model name
+    default: codellama
+    required: false
+  prompt:
+    description: Input prompt before the PR diff
+    default: 'Summarize the code diff concisely:'
+    required: false
+  token:
+    description: GitHub token
+    default: ${{ github.token }}
     required: false
-    default: 1.2.3
 
 runs:
   using: composite
   steps:
-    - name: Print version
-      shell: bash
-      run: |
-        echo 'version: ${{ inputs.version }}'
+      - name: Setup ollama
+        uses: ai-action/setup-ollama@v1
+
+      - name: Checkout repository
+        uses: actions/checkout@v4
+
+      - name: Summarize pull request
+        shell: bash
+        run: |
+          PROMPT=$(printf '%s\n%s' "$PROMPT" "$(gh pr diff $PR_NUMBER)")
+          RESPONSE=$(ollama run $MODEL "$PROMPT" | sed 's/^/> /')
+          BODY=$(gh pr view $PR_NUMBER --json body --jq .body)
+          COMMENT_START='<!--pull-request-summary-start-->'
+          COMMENT_END='<!--pull-request-summary-end-->'
+
+          if [[ "$BODY" == *"$COMMENT_START"* ]]; then
+            # delete between patterns (inclusive)
+            BODY=$(echo "$BODY" | sed "/$COMMENT_START/,/$COMMENT_END/d")
+          fi
+
+          BODY=$(printf '%s\n\n%s\n\n> [!NOTE]\n%s\n\n%s\n' "$BODY" $COMMENT_START "$RESPONSE" $COMMENT_END)
+          gh pr edit $PR_NUMBER --body "$BODY"
+        env:
+          GH_TOKEN: ${{ inputs.token }}
+          PR_NUMBER: ${{ github.event.pull_request.number }}
+          PROMPT: ${{ inputs.prompt }}
+          MODEL: ${{ inputs.model }}
 
 branding:
   icon: code