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Sweep 03 Nov 2026 · 22:27Z Build v2.1.318 536 read Stable v2.1.311 Latest v2.1.318 Next v2.1.318 Feeds RSS JSON llms.txt llms-full.txt Unofficial
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Claude Code v2.1.317 ·

MCP tool error messages are now built by one shared step

When an MCP tool call fails, Claude Code now works out the error code and message in one shared step instead of building them in place

Under the hood Internal Changes
JSON All of v2.1.317
Under the hoodTier: how much it should matter to you
1Useful: my rating, 1 to 5
0Signal: worth watching, 1 to 5
MCPArea: what it touches
Internal ChangesKind: in v2.1.317,
Internal ChangesSection of the release

Unclear It is not clear what wording Claude now sees when an MCP tool call fails.

What

MCP servers are outside programs that give Claude Code extra tools. When a call to one of those tools fails, Claude Code works out an error code and a message to describe the failure. That used to happen in place, producing messages such as "Server answered HTTP" followed by a status number, or "Connection error". Those messages are no longer built here. A shared step now works out the error code, the message and any extra data.

Why

The error text Claude sees when an MCP tool fails may read differently than before.

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 wording Claude now sees when an MCP tool call fails.

See this entry in the whole of v2.1.317 →

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