Scale to many tools with tool search changedagent-sdk/tool-search
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4242| `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. |
4343| `false` | Tool search is off. All tool definitions are loaded into context on every turn. |
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45Setting [`CLAUDE_CODE_DISABLE_EXPERIMENTAL_BETAS`](/docs/en/env-vars) keeps tool search off. You can't override it by setting `ENABLE_TOOL_SEARCH` yourself. Your organization can keep tool search on through [managed settings](/docs/en/managed-settings), on Claude Code v2.1.227 or later. [Disable pre-release capabilities](/docs/en/llm-gateway-protocol#disable-pre-release-capabilities) covers where the override applies and what the variable strips.
45Setting [`CLAUDE_CODE_DISABLE_EXPERIMENTAL_BETAS`](/docs/en/env-vars) keeps tool search off. You can't override it by setting `ENABLE_TOOL_SEARCH` yourself. On Claude Code v2.1.227 or later, your organization can keep tool search on under this variable through [managed settings](/docs/en/managed-settings). In a session that [gets the HIPAA configuration](/docs/en/hipaa-setup#check-how-developers-sign-in-and-connect), tool search is off, and neither `ENABLE_TOOL_SEARCH` nor managed settings turns it back on. [Disable pre-release capabilities](/docs/en/llm-gateway-protocol#disable-pre-release-capabilities) covers where the override applies and what the variable strips.
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4747Tool search applies to all registered tools, whether they come from remote MCP servers or [custom SDK MCP servers](/docs/en/agent-sdk/custom-tools). When you use `auto`, the SDK counts every definition that tool search can defer toward one combined threshold: each MCP tool that isn't marked [`alwaysLoad`](/docs/en/mcp#exempt-a-server-from-deferral), from any server, plus the built-in tools that load on demand. The SDK loads core built-in tools such as Bash, Read, and Edit upfront and doesn't count them toward the threshold. A [mod](/docs/en/plugins/mods/reference#tools) in one of your plugins can also defer a tool or load it upfront, which changes that count.
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