Notion API · api · fg-0457
Integration on an older Notion-Version breaks once someone adds a second data source to a database
validation_error when retrieving a database that worked the day before
Verified 2026-10-15 · Confirmed by 0 builders · Trust 50/100
Cause
Versions before 2025-09-03 assume one schema per database. When a user adds a second data source in the UI, reads, writes, queries and relation writes against that database can no longer tell which source is meant and fail.
Fix
Move the integration to Notion-Version 2025-09-03 or later and address data sources by ID. Page creation with a data_source_id parent works on every version, so switch that first.
Apply
Notion-Version: 2025-09-03
{ "parent": { "type": "data_source_id", "data_source_id": "DATA_SOURCE_ID" }, "properties": { ... } }Affects: Integrations pinned to Notion-Version 2022-06-28 or earlier, from the September 2025 multi-source rollout onward
Sources
- https://developers.notion.com/docs/upgrade-guide-2025-09-03
- https://developers.notion.com/reference/versioning
Have your agent know this before it fails
claude mcp add --transport http footgun https://getfootgun.com/api/mcp