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Tools

Voice agents can use any Tool from the workspace tool library — but with one structural requirement: tools attached to a voice agent must be in Sync mode.

Why Sync mode​

Voice is latency-sensitive. The standard async tool execution path runs through a queue, which is fine for a chat agent but introduces hesitation a user can hear on a phone call. Sync mode executes tool steps immediately to keep tool calls inside the voice latency budget.

Sync mode is a Tool-level setting, configured on the Tool itself in the Run Mode and Limits drawer (accessed from the top-right hamburger menu on the Tool edit screen). The toggle has this tooltip:

Sync mode executes tool steps immediately to minimize latency. This is recommended for voice agents but may enforce stricter execution limits.

Lower defaults and stricter limits​

Because voice is latency-sensitive, voice agents enforce lower defaults and lower maximum limits for tool usage limit and timeout than standard agents. An inline note is shown in the Tool section of the configuration screen:

Voice agents have lower tool timeout limits to maintain call latency.

Per-tool settings still configurable from the voice agent:

  • Usage limit — how many times the tool can be called per call.
  • Timeout — how long the platform waits for the tool to complete before giving up.

What's disabled when Sync mode is on​

Sync mode cannot safely support nested orchestration, so these node types are not available in a Sync-mode tool — they don't appear in the node picker:

  • SimplAI Tools
  • SimplAI Agents
  • Agent Create Node
  • MCP Tools

If a tool already contains any of the above nodes, the Sync mode toggle on the Tool edit screen is disabled, and a message explains why Sync mode cannot be enabled. Remove or replace the offending nodes to enable Sync mode.

Attaching tools — the UI​

In the voice agent configuration screen, the Tool selection picker shows all published tools. Tools that are not eligible for voice (i.e., the Tool is not in Sync mode and contains nested-orchestration nodes that prevent enabling Sync mode) are disabled with a tooltip:

This tool is not eligible for voice agents.

A Learn more link explains that voice agents require synchronous tools and lists the unsupported node types.

Auto-enabling Sync mode​

If you pick a tool that is compatible with Sync mode but currently has Sync mode off, the platform prompts a confirmation dialog explaining:

  • Nested orchestration nodes will no longer be available in the tool.
  • The tool will run under stricter execution limits for voice latency.

On confirmation, Sync mode is automatically enabled for that tool. (This affects the Tool everywhere — including any non-voice uses.)

In the run trace​

Each tool call appears as its own span in the run trace, under the LLM reasoning span that called it. The span shows timing and status. In Sync mode, there should be near-zero gap between the Tool span ending and the next LLM reasoning span starting — if you see a gap there, file it as a Sync flow regression.

See Run history & traces for how tool spans appear in the trace view.