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Auto-Summary Function

examples/functions/auto-summary/README.md

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Auto-Summary Function

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Problem

Content teams often need concise summaries of long-form content (like blog posts or articles) for previews, SEO, or editorial workflows. Manually writing these summaries is time-consuming and inconsistent, especially as content volume grows.

Solution

This example demonstrates how to use a Sanity Function to automatically generate a summary for a document's content field using Sanity's Agent Actions. When a post's content is changed the function generates a summary (up to 250 words) and writes it to the autoSummary field.

Benefits

  • Saves 2-3 minutes per post by eliminating manual summary writing
  • Saves editorial time by automating summary creation for every post
  • Improves consistency in summary style and length across all content
  • Scales easily as content volume increases, with no extra manual effort
  • Reduces editorial overhead for content teams

Compatible Templates

This function is built to be compatible with any of the official "clean" templates. We recommend testing the function out in one of those after you have installed them locally.

Adding the autoSummary field to your schema

If you're using the nextjs-clean template, you'll need to add a tags field to your post schema:

  1. Open studio/src/schemaTypes/documents/post.ts
  2. Add this field to the fields array:
typescript
defineField({
  name: 'autoSummary',
  title: 'Auto Summary',
  type: 'text',
  description: 'Summary will be automatically generated when you publish a post',
}),
  1. Deploy your updated schema:
bash
# /studio
npx sanity schema deploy

Implementation

Important: Run these commands from the root of your project (not inside the studio/ folder).

  1. Initialize the example

    Run this if you haven't initialized blueprints:

    bash
    npx sanity blueprints init

    You'll be prompted to select your organization and Sanity studio.

    Then run:

    bash
    npx sanity blueprints add function --example auto-summary

  2. Add configuration to your blueprint

    Add the following resource to your sanity.blueprint.ts:

    ts
    defineDocumentFunction({
  src: './functions/auto-summary',
  memory: 2,
  timeout: 30,
  name: 'auto-summary',
  event: {
    on: ['create', 'update'],
    filter:
      "_type == 'post' && (delta::changedAny(content) || (delta::operation() == 'create' && defined(content)))",
    projection: '{_id}',
  },
})

  3. Install dependencies

    Install dependencies in the project root:

    bash
    npm install

  4. Make sure you have a schema deployed

From the studio folder, run:

bash
# In the studio/ folder
npx sanity schema deploy

Testing the function locally

You can test the auto-summary function locally using the Sanity CLI before deploying it to production.

Simple Testing Command

Test the function with an existing document ID from your dataset:

bash
npx sanity functions test auto-summary --document-id <insert-document-id> --dataset production --with-user-token

Replace <insert-document-id> with an actual document ID from your dataset and production with your dataset name.

Interactive Development Mode

Start the development server for interactive testing:

bash
npx sanity functions dev

Testing Tips

  • Use real document IDs - Document functions require IDs that exist in your dataset
  • Use Node.js v22.x locally to match production runtime
  • Test edge cases like posts without content or with existing summaries
  • Check function logs in CLI output for debugging
  • Test without AI calls first by setting noWrite: true in the function
  • Create test content - If you don't have posts without summaries, create some test documents first

Requirements

  • A Sanity project with Functions enabled
  • A schema with a post document type containing:
    • A content field (for content analysis)
    • A autoSummary field (string or text) (for storing generated summary)
  • Access to Sanity's AI capabilities
  • Node.js v22.x for local testing

Usage Example

When a content editor creates a blog post or modifies the 'content' field, the function automatically:

  1. Analyzes the post's content field using AI
  2. Generates a summary (max 250 words) based on the content field
  3. Applies the summary directly to the document

Result: Content creators get consistent, relevant summaries without manual effort.

Customization

  • Change the instruction string in index.ts to adjust the summary style, length, or language.
  • Modify the filter in the blueprint resource to target different document types or conditions.
  • Set noWrite: false in the function to automatically write the summary to the document in production.

Troubleshooting

Error: "Error occurred during summary generation"

  • Cause: The AI action may fail if the document is missing a content field or if there are API issues.
  • Solution: Ensure the document has a valid content field and check your Sanity project configuration.