Tools

Tools are callable functions exposed to the live model.

Execution modes

• inline: blocking, result returned in-turn
• background: async handoff to subagent

On gemini-3.8-live — the default Live model — every function is declared BLOCKING unless the tool sets behavior or the session sets functionBehavior. That model would otherwise run an undeclared call NON_BLOCKING and end its turn before the result exists. Other Live models, including gemini-3.1-flash-live-preview and the 2.5 native-audio models, are sent no behavior and keep the server default they were measured with. Set 'NON_BLOCKING' to opt into asynchronous calls, or 'BLOCKING' to ask for it on a model that does not get it by default.

Tool basics

Each tool defines:

• name, description
• parameters (zod schema)
• execution
• execute(args, ctx)

Artifact Pipeline (Cross-Tool Data Flow)

The framework supports per-session artifact sharing across tools and subagents.

Use this when one tool generates binary data (image/document) and another tool needs it later (email, analysis, relay).

Typical flow:

1. Generator tool stores artifact in registry.
2. Registry returns artifactId.
3. Downstream tool receives artifactId and materializes/forwards data.

This avoids embedding base64 into prompt text and keeps handoffs structured.