AWS today announced Amazon S3 annotations, a new metadata capability that lets you attach up to 1,000 named annotations per object, each up to 1 MB in size, totaling up to 1 GB per object. Annotations support JSON, XML, YAML, or plain text, and can be modified or deleted without rewriting the object. The feature is designed for AI agent workflows that need rich, evolving context at scale.

Key Details

• Scale: 1,000 annotations per object, each 1 MB max, total 1 GB per object.
• Formats: JSON, XML, YAML, plain text.
• Mutability: Add, modify, or delete annotations at any time without touching the object data.
• Lifecycle: Annotations move with the object during copy, replication, and cross-region transfers; removed on object deletion.
• Queryability: When S3 Metadata is enabled, annotations flow into annotation tables queryable via Amazon Athena and other analytics engines. AI agents can discover data using natural language through the S3 Tables MCP server.
• Storage classes: Query annotations on objects in any storage class, including Glacier, without restoring objects or paying retrieval charges.

Using the CLI

Create a JSON annotation on an existing object:

# Create a JSON file with technical metadata
cat > mediainfo.json << 'EOF'
{"codec":"H.265","resolution":"3840x2160","audio_tracks":8,"frame_rate":29.97}
EOF

Attach it as an annotation
aws s3api put-object-annotation 
  --bucket my-media-bucket 
  --key videos/documentary-2026.mp4 
  --annotation-name mediainfo 
  --annotation-payload ./mediainfo.json

Attach a plain-text AI-generated summary as a separate annotation:

echo "A 90-minute nature documentary..." > summary.txt
aws s3api put-object-annotation 
  --bucket my-media-bucket 
  --key videos/documentary-2026.mp4 
  --annotation-name ai-summary 
  --annotation-payload ./summary.txt

Use Cases

• Media & Entertainment: Track transcripts, content moderation results, subtitles, and licensing metadata as separate annotations on video assets.
• Financial Services: Attach AI-generated investment summaries to research documents for autonomous research agents.
• Life Sciences: Annotate clinical trial data with regulatory status, patient cohort details, and approval chains — accessible even in Glacier without retrieval charges.

Permissions

IAM policies need s3:PutObjectAnnotation and s3:GetObjectAnnotation actions. No changes to the object itself are required.

Compared to Existing Metadata