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Sweep 22 Oct 2026 · 04:32Z Build v2.1.308 527 read Stable v2.1.308 Latest v2.1.308 Next v2.1.308 Feeds RSS JSON llms.txt llms-full.txt Unofficial
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Claude Code v2.1.301 ·

MCP tool results can be kept from the model, with a size limit

An MCP tool call made through the control channel can mark its result as not for the model, and too-large results now return an error text

Use it now New Features
JSON All of v2.1.301
Use it nowTier: how much it should matter to you
3Useful: my rating, 1 to 5
2Signal: worth watching, 1 to 5
SDKArea: what it touches
New FeaturesKind: in v2.1.301,
What probably matters to youSection of the release

Unclear It is not clear what turns the not-for-model setting on or whether any program sends it yet.

What

MCP servers are external programs that give Claude Code extra tools. When a program that embeds Claude Code asks it to call an MCP tool directly, the request can now carry a setting saying the result is not meant for the model. If the result is too large, Claude Code sends back a fixed error message instead of the result itself.

Before, results were always passed back in full, with no size check.

Why

Programs that embed Claude Code through the SDK (the toolkit for building on Claude Code) or run it remotely may now get an error message back instead of the content of a large MCP tool result.

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 doubtIt is not clear what turns the not-for-model setting on or whether any program sends it yet.

See this entry in the whole of v2.1.301 →

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