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HomeDocsClaude Code CLI 21 Oct 2026
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Connect Claude Code to tools via MCP changedmcp

Nearest release: v2.1.306, published 3 hours before upstream edited the page. Shown because the two are within 24 hours of each other. Nothing here says the release caused the edit.

Upstream edited this page at 21 Oct 2026 06:28 UTC, give or take a minute or two: the time comes from Anthropic’s own sitemap rather than from a commit. This site recorded the change at 21 Oct 2026 06:37 UTC.

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First seen 14 Aug 2026 this site's first read of the page
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#### Tools that stay deferred below the `ENABLE_TOOL_SEARCH=auto` threshold

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15031503| :- | :- |
15041504| (unset) | All MCP tools deferred and loaded on demand. Loaded upfront on models earlier than Opus 4 and Sonnet 4, on the [earlier Agent Platform models](#configure-tool-search), and on Microsoft Foundry deployments hosted on Azure |
15051505| `true` | MCP tools deferred, with the same fallbacks as (unset) |
1506| `auto` | Threshold mode: Claude Code loads the tools it would otherwise defer upfront while their definitions total less than 10% of the context window, and defers all of them once the definitions reach 10% |
1506| `auto` | Threshold mode. Tools that would otherwise be deferred load upfront while their definitions total under 10% of the context window. At 10% or more, tool search turns on, and those tools can [stay deferred](#tools-that-stay-deferred-below-the-threshold) even if the total falls under 10% |
15071507| `auto:N` | Threshold mode with a custom percentage, where `N` is 0-100. For example, `auto:5` for 5% |
15081508| `false` | All MCP tools loaded upfront, no deferral |
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15411541When `ANTHROPIC_BASE_URL` points to a gateway, tool search is on by default, so requests include `defer_loading` tool fields and `tool_reference` blocks for the gateway to forward. While tool search is on, MCP tools are [deferred](#scale-with-mcp-tool-search). To load every tool upfront instead, set `ENABLE_TOOL_SEARCH=false` in your shell or your [settings `env`](/docs/en/settings-reference#env). Before v2.1.304, tool search was off behind a gateway unless `ENABLE_TOOL_SEARCH` was `true`, `auto`, or `auto:N`.
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15431543On v2.1.305 or later, Claude Code can [retry a request without tool search](/docs/en/llm-gateway-protocol#retry-without-tool-search) after a `400` or `422` whose cause it doesn't recognize. When the retry works, nothing shows on screen and you don't need to do anything: MCP tools load upfront instead. Claude Code tries tool search again later, at the cost of another rejected request. To skip those requests, set `ENABLE_TOOL_SEARCH=false`.
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1545#### Tools that stay deferred below the `ENABLE_TOOL_SEARCH=auto` threshold
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1547If [`/context`](/docs/en/commands#all-commands) labels tools `(deferred)` or `(loaded on-demand)` though their definitions total under the `auto` threshold, tool search was already on in this conversation and stayed on. The total can drop later, for example while MCP servers reconnect after you resume a session. You don't need to do anything: Claude loads each of those tools when a task needs it.
15441548 
15451549### Exempt a server from deferral
15461550 
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