DisclaimerUnofficial, and not affiliated with Anthropic. Nearly all of this is read straight out of what ships: npm bundles, captured prompts, published docs. Anthropic's own notes go in verbatim, marked as theirs. The rest is my reading, and every entry carries the strings behind it. If one looks wrong, vote it down and say why.
Deferred tools are now announced through system-reminder messages in the conversation rather than a static list, controlled by the tengu_glacier_2xr feature flag. This makes tool availability more dynamic and context-aware.
Evidence
Deferred tools announcement (search for "Deferred tools are announced via system-reminder messages")
Strings lifted out of the shipped bundle, so the claim above can be checked against them.