Scale to many tools with tool search changedagent-sdk/tool-search
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1414Tool search is on by default, with the exceptions listed in [Configure tool search](#configure-tool-search).
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16When it is active, tool definitions are withheld from the context window. The agent receives a summary of available tools and searches for relevant ones when the task requires a capability not already loaded. Up to five of the most relevant tools are loaded into context by default, where they stay available for subsequent turns. If the conversation is long enough that the SDK compacts earlier messages to free space, previously discovered tools may be removed, and the agent searches again as needed.
16When it is active, tool definitions are withheld from the context window. The agent receives a summary of available tools and searches for relevant ones when the task requires a capability not already loaded. Up to five of the most relevant tools are loaded into context by default, where they stay available for subsequent turns. When the SDK compacts earlier messages to free space, it keeps the discovered tools loaded.
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1818Tool search adds one extra round-trip the first time Claude discovers a tool (the search step), but for large tool sets this is offset by smaller context on every turn. With fewer than \~10 tools whose definitions fit comfortably in the context window, loading everything upfront is typically faster.
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