Under the hoodTier: how much it should matter to you
1Useful: my rating, 1 to 5
1Signal: worth watching, 1 to 5
HooksArea: what it touches
Internal ChangesKind: in v2.1.275,
Internal ChangesSection of the release
Unclear What practical difference the new 'measure' combinator makes to hook authors versus the previous 'carry' function is not stated.
What
The internal descriptor for the tool.call hook event, used alongside PreToolUse (a hook point that runs before a tool call executes and can block it), now includes a measure function. This function combines the context of one event with the contexts of a list of related events, replacing what was previously a simpler carry function.
Why
This is internal plumbing for how hook event context is assembled; the finding doesn't indicate a directly user-visible change.
The entry above is what we published on the day. These lines were added later, as Anthropic's own pages caught up, and they sit beside the original rather than replacing it.
Added sinceA small documentation edit on Plugin commands reference touched a line naming tool.call after this was published.* `gatingHooks`: whether each [mod](/docs/en/plugins/mods/overview) hook that can refuse an action, such as a `tool.call` hook, has a [`.catch` handler](/docs/en/plugins/mods/events#handle-a-hook-that-fails). Each item gives `module`, `pat…plugins/cli-referencesee the edit
Confirmed sinceAnthropic's documentation has since written up tool.call, on Configure a custom OpenTelemetry collector.| `tool.caller` | `direct` for tools the add-in runs, or `server_tool` for tools the model provider runs |office-agents/opentelemetrysee the edit
How sure we are
Something disagreesSomething we can check disagrees with this entry, or the writer said they could not settle it.
The writer flagged doubtWhat practical difference the new 'measure' combinator makes to hook authors versus the previous 'carry' function is not stated.
Anthropic's documentation agreesAnthropic's documentation has since written up tool.call, on Configure a custom OpenTelemetry collector.
