ToolSearch
A mechanism in MCP clients that loads tool JSON Schemas on demand. Only tool names are listed in the prompt; when the model needs a tool, it calls a search tool to pull the target schema into context, thereby reducing context consumption.
Timeline (last 90 days)
Claude Code v2.1.304 introduced a regression: when an endpoint or gateway rejects tool search, or the gateway does not include it in --tools, every request to Vertex, Bedrock and other providers fails.
v2.1.302 fixes the issue where tools added mid-session, when reloaded via ToolSearch or after compaction, reported prompt cache misses.
For Claude Code with 100 tools, enabling ToolSearch used 59% fewer input tokens per run than disabling search (19.9k vs 48.6k), but at list prices enabling search cost $0.047 per run while disabling search cost $0.038.
The extra ToolSearch calls make Claude Code more expensive than full loading below about 19 tools and cheaper above 19.
All Facts (4)
Claude Code v2.1.304 introduced a regression: when an endpoint or gateway rejects tool search, or the gateway does not include it in --tools, every request to Vertex, Bedrock and other providers fails.
50%Unverifiedv2.1.302 fixes the issue where tools added mid-session, when reloaded via ToolSearch or after compaction, reported prompt cache misses.
50%UnverifiedFor Claude Code with 100 tools, enabling ToolSearch used 59% fewer input tokens per run than disabling search (19.9k vs 48.6k), but at list prices enabling search cost $0.047 per run while disabling search cost $0.038.
50%UnverifiedThe extra ToolSearch calls make Claude Code more expensive than full loading below about 19 tools and cheaper above 19.
50%