Scale to many tools with tool search changedagent-sdk/tool-search
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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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4242| :- | :- |
4343| (unset) | Tool search is on, with tool definitions deferred and discovered on demand. Falls back to loading 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. |
4444| `true` | Tool search is on, with the same fallbacks as (unset). |
45| `auto` | Counts the tokens in the tool definitions that tool search can defer and compares the total against the model's context window. When the total reaches 10% of the window, tool search activates. Below that, the SDK loads every tool definition into context upfront. |
45| `auto` | Tool search is off, and tool definitions load upfront, until the definitions it can defer reach 10% of the model's context window. Tool search then activates, and can [stay on in the same conversation](/docs/en/mcp#tools-that-stay-deferred-below-the-threshold) even if those definitions later drop below 10%. |
4646| `auto:N` | Same as `auto` with a custom percentage. `auto:5` activates when those definitions reach 5% of the context window. Lower values activate sooner. |
4747| `false` | Tool search is off. All tool definitions are loaded into context on every turn. |
4848
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