Tool Search

Tool Search keeps unused MCP tool definitions out of each request. This leaves more model context for your work while Kiro loads the tools it needs.

Kiro IDE 1.3 and later use Tool Search automatically. Local V3 sessions in Kiro CLI 2.31 and later use it by default. Tool Search has no effect when you have no MCP servers configured.

In V2 sessions, Tool Search remains opt-in. Enable it with:

kiro-cli settings toolSearch.enabled true

In V2, Tool Search activates when MCP tool definitions cross either configured threshold: 5% of the context window or 50,000 tokens by default. To activate it whenever any MCP tools are present, set both thresholds to 0:

kiro-cli settings toolSearch.minPct 0
kiro-cli settings toolSearch.minTokens 0

When both thresholds are set, either one can activate Tool Search. When both are 0, any configured MCP tool activates it.

V3 loads MCP tools on demand by default. Kiro CLI 2.31.1 and later applies saved toolSearch.enabled, toolSearch.minPct, and toolSearch.minTokens values to both interactive and non-interactive V3 runs. It applies saved thresholds only when toolSearch.enabled is also saved.

When Tool Search is active:

• IDE and local V3 activity can show tool_load before tool_call for an MCP tool
• In V2, /tools shows lower MCP tool token use than preloading every definition

1. Indexing: Kiro indexes the names and descriptions of tools from connected MCP servers.
2. Deferred catalog: The model receives a compact list instead of every full tool definition.
3. Definition loading: Kiro loads a needed tool's full description and input schema.
4. Tool call: Kiro calls the loaded tool through the normal permission and Hook checks.

In IDE and local V3 sessions, tool_load loads exact tool IDs and tool_call runs them. V2 uses the legacy tool_search path when you enable it.

• Built-in tools: Tools included with Kiro
• Settings reference: Tool Search settings
• MCP configuration: Configure MCP servers
• Terminal UI: View tool activity