Custom Tools
Agent Responses to Tools
Configure when and how your agent responds after tool calls - whether to speak immediately, listen for input, or speak conditionally.
Post-Tool Call Behavior
By default, the agent speaks again immediately after a tool call. This is typically the desired behavior for tools that gather information since the agent can immediately respond based on the information retrieved. However, this may make less sense for other tools. For example, if your agent is gathering information for the user and you have a tool that allows the agent to store what’s been gathered so far, you may want the agent to speak either before or after the tool but not both. Ultravox Realtime allows you to define how the agent reacts after a tool call by setting theagent reaction. A default can be set on the tool itself or you can use either the X-Ultravox-Agent-Reaction header (for http tools) or the agent_reaction field on the tool result message (for client and data connection tools) similar to how you’d set a response type (see above).
| Reaction | Description |
|---|---|
| speaks | Agent will speak immediately after the tool call returns. This is the default behavior if agent reaction is not set. Should be used for tools that gather information. |
| listens | Agent listens for user input and doesn’t speak. |
| speaks-once | Agent speaks only if it didn’t speak immediately before the tool call. Prevents agent repeating things before and after the tool call. |