Claude API beta lets tools be defined inside mid-conversation system messages
Tech · Releases · Tue, September 22, 2026
With the inline-tools-2026-09-15 beta header, a tool_addition block can carry a full tool definition, so agents can add tools, change schemas or upgrade server tools mid-conversation without invalidating the prompt cache. The same header co
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Also on Sep 22, 2026
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- anthropic
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- From the Releases API (releases.fru.dev), which reads each vendor's changelog.
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- Changes
- 2026-09-25: added to 2026-09-22