# Talking while waiting (/en/ai/build/shape-the-conversation/filler-words) > For AI agents: see the complete documentation index at [llms.txt](/llms.txt). In conversational AI, delays in LLM responses may cause users to wonder if the agent is still processing, repeat their question, or disengage entirely. Filler words address this by playing short phrases while the agent waits for the LLM to generate a response. This keeps the conversation flowing, reduces user anxiety, and creates a more human-like interaction. Common use cases for filler words include: * **MCP tool calls**: When the agent invokes tools through [MCP servers](/en/api-reference/api-ref/conversational-ai/join#properties-llm-mcp-servers), response times can increase significantly. Filler words bridge this gap while the agent waits for tool results. * **Complex queries**: Queries that require more LLM processing time benefit from a brief acknowledgment to signal that the agent is working on a response. * **Customer service scenarios**: In support interactions, filler words such as "Let me look into that for you" reassure users that their request is being handled. ## Prerequisites [#prerequisites] Use the [Agora CLI](/en/introduction/agora-cli) to create or select an Agora project, enable RTC and Conversational AI, and verify project readiness: ```bash agora login agora project create conv-ai-tutorial --feature rtc --feature convoai agora project use conv-ai-tutorial agora project doctor --feature convoai ``` You also need a working Conversational AI Engine project. If you don't have one yet, follow the [quickstart](../../get-started/quickstart) to set one up. ## Implementation [#implementation] ### Enable filler words [#enable-filler-words] To enable filler words, add the `filler_words` object to `properties` when calling the [Start a conversational AI agent](/en/api-reference/api-ref/conversational-ai/join) API. Set `enable` to `true`: ```json "properties": { "filler_words": { "enable": true, "trigger": { ... }, "content": { ... } } } ``` When enabled, the agent plays filler phrases during periods of silence while waiting for LLM output. Filler word playback follows these rules: * **Playback order**: When multiple filler words or LLM responses are waiting to be played, they are played in the order they arrive. * **Interruption control**: Filler words inherit the interruption mode setting from the global configuration in `turn_detection.config`. ### Configure [#configure] The `filler_words` object contains three main sections: `enable`, `trigger`, and `content`. #### Trigger [#trigger] The `trigger` object defines when the agent plays filler words. Currently, the `fixed_time` mode is supported. In this mode, filler words play when the LLM response wait time exceeds a specified threshold. | Parameter | Type | Range | Description | | -------------------------------------------- | ------- | ------------ | ------------------------------------------------------------------------------------------------------------------------------------- | | `trigger.mode` | String | `fixed_time` | Trigger mode. Currently only `fixed_time` is supported. | | `trigger.fixed_time_config.response_wait_ms` | Integer | 100-10000 | LLM response wait threshold in milliseconds. The agent plays a filler phrase when the LLM takes longer than this duration to respond. | Choose a `response_wait_ms` value based on your use case: * **Lower values** (500-1000 ms): Better for fast-paced interactions where silence is more noticeable. * **Higher values** (1500-3000 ms): Suitable for scenarios where users expect some processing time, such as complex queries or data lookups. #### Content [#content] The `content` object defines the source and selection behavior of filler phrases. Currently, the `static` mode is supported, which uses a predefined list of phrases. | Parameter | Type | Description | | -------------------------------------- | -------------- | ------------------------------------------------------------------------- | | `content.mode` | String | Content mode. Currently only `static` is supported. | | `content.static_config.phrases` | Array\[String] | List of filler phrases. Maximum 100 phrases, each up to 50 English words. | | `content.static_config.selection_rule` | String | Selection rule for choosing phrases. Accepts `shuffle` or `round_robin`. | Selection rules: * `shuffle`: Randomly selects phrases without repeating until all phrases have been used. After a full cycle, the list is reshuffled and a new round begins. * `round_robin`: Selects phrases sequentially from the list. After all phrases are played, a new cycle begins. ### Sample configuration [#sample-configuration] The following example configures filler words that play a random phrase when the LLM takes longer than 1.5 seconds to respond. Python SDK TypeScript SDK Go SDK REST API ```python from agora_agent import Agent from agora_agent.agentkit import ( FillerWordsConfig, FillerWordsTrigger, FillerWordsTriggerFixedTimeConfig, FillerWordsContent, FillerWordsContentStaticConfig, ) # client is your configured Agora client agent = ( Agent(client) .with_stt(...) # configure your STT vendor .with_llm(...) # configure your LLM vendor .with_tts(...) # configure your TTS vendor .with_filler_words(FillerWordsConfig( enable=True, trigger=FillerWordsTrigger( mode='fixed_time', fixed_time_config=FillerWordsTriggerFixedTimeConfig( response_wait_ms=1500, ), ), content=FillerWordsContent( mode='static', static_config=FillerWordsContentStaticConfig( phrases=[ 'Let me look into that.', 'One moment, please.', 'Sure, give me a second.', 'Hmmm, let me check.', ], selection_rule='shuffle', ), ), )) ) ``` ```typescript import { Agent } from 'agora-agents'; // client is your configured Agora client const agent = new Agent({ client }) .withStt(/* configure your STT vendor */) .withLlm(/* configure your LLM vendor */) .withTts(/* configure your TTS vendor */) .withFillerWords({ enable: true, trigger: { mode: 'fixed_time', fixed_time_config: { response_wait_ms: 1500, }, }, content: { mode: 'static', static_config: { phrases: [ 'Let me look into that.', 'One moment, please.', 'Sure, give me a second.', 'Hmmm, let me check.', ], selection_rule: 'shuffle', }, }, }); ``` ```go import ( "github.com/AgoraIO/agora-agents-go/v2/agentkit" Agora "github.com/AgoraIO/agora-agents-go/v2" ) // client is your configured *agentkit.AgoraClient agent := agentkit.NewAgent(client). WithStt(/* configure your STT vendor */). WithLlm(/* configure your LLM vendor */). WithTts(/* configure your TTS vendor */). WithFillerWords(&agentkit.FillerWordsConfig{ Enable: Agora.Bool(true), Trigger: &agentkit.FillerWordsTrigger{ Mode: Agora.String("fixed_time"), FixedTimeConfig: &agentkit.FillerWordsTriggerFixedTimeConfig{ ResponseWaitMs: Agora.Int(1500), }, }, Content: &agentkit.FillerWordsContent{ Mode: Agora.String("static"), StaticConfig: &agentkit.FillerWordsContentStaticConfig{ Phrases: []string{ "Let me look into that.", "One moment, please.", "Sure, give me a second.", "Hmmm, let me check.", }, SelectionRule: agentkit.FillerWordsSelectionRuleShuffle.Ptr(), }, }, }) ``` Add the following `filler_words` object to `properties` in your [Start a conversational AI agent](/en/api-reference/api-ref/conversational-ai/join) request body: ```json "filler_words": { "enable": true, "trigger": { "mode": "fixed_time", "fixed_time_config": { "response_wait_ms": 1500 } }, "content": { "mode": "static", "static_config": { "phrases": [ "Let me look into that.", "One moment, please.", "Sure, give me a second.", "Hmmm, let me check." ], "selection_rule": "shuffle" } } } ``` ## Best practices [#best-practices] Keep the following tips in mind when configuring filler words: * **Keep phrases short and natural**: Use brief, conversational phrases that sound like something a person would say. * **Match phrasing to your use case**: For customer support agents, use reassuring phrases like "Let me look into that for you." For casual assistants, use informal phrases like "Hmm, one sec." * **Tune the trigger threshold**: Start with a `response_wait_ms` of 1500 ms and adjust based on your LLM's typical response time. If your agent frequently invokes tools, consider a lower threshold to cover longer processing times. * **Provide enough variety**: Include at least 4-6 phrases to avoid sounding repetitive. Use `shuffle` selection to maximize variety across conversation turns. ## References [#references] * [Start a conversational AI agent](/en/api-reference/api-ref/conversational-ai/join)