Debugging voice agents

Learn to identify, diagnose, and fix common issues with your voice assistants and workflows

Overview

Voice agents involve multiple AI systems working together—speech recognition, language models, and voice synthesis. When something goes wrong, systematic debugging helps you quickly identify and fix the root cause.

Most common issues fall into these categories:

Speech & Understanding
  • Agent doesn’t understand user input correctly
  • Responses are inappropriate or inconsistent
  • Agent sounds robotic or unnatural
Technical & Integration
  • Call quality issues or audio problems
  • Tool integrations failing or returning errors
  • Workflow logic not executing as expected

Quick diagnostics

Start with these immediate checks before diving deeper:

1

Test in dashboard

Test your voice agent directly in the dashboard:

Assistants

Click “Talk to Assistant” to test

Workflows

Click “Call” to test workflow

Benefits:

  • Eliminates phone network variables
  • Provides real-time transcript view
  • Shows tool execution results immediately
2

Check logs

Navigate to the Observe section in your dashboard sidebar:

Call Logs

Review call transcripts, durations, and error messages

API Logs

Check API requests and responses for integration issues

Webhook Logs

Verify webhook deliveries and server responses

3

Test individual components

Use dashboard testing features:

Voice Test Suites

Automated testing for assistants

Tool Testing

Test tools with sample data

4

Verify provider status

Check if AI service providers are experiencing issues:

Core Services:

Provider Status Pages:

Dashboard debugging resources

The Vapi dashboard provides powerful debugging features to help you identify and fix issues quickly:

Call Logs

Navigate to Observe > Call Logs to:

  • Review complete call transcripts
  • Check call duration and completion status
  • Identify where calls failed or ended unexpectedly
  • See tool execution results and errors
  • Analyze conversation flow in workflows

API Logs

Navigate to Observe > API Logs to:

  • Monitor all API requests and responses
  • Check for authentication errors
  • Verify request payloads and response codes
  • Debug integration issues with external services

Webhook Logs

Navigate to Observe > Webhook Logs to:

  • Verify webhook deliveries to your server
  • Check server response codes and timing
  • Debug webhook authentication issues
  • Monitor event delivery failures

Voice Test Suites

Navigate to Test > Voice Test Suites to:

  • Run automated tests on your assistants (not available for workflows)
  • Test conversation flows with predefined scenarios
  • Verify assistant behavior across different inputs
  • Monitor performance over time

Tool Testing

For any tool in your Tools section:

  • Navigate to Tools > [Select Tool]
  • Use the Test button to send sample payloads
  • Verify tool responses and error handling
  • Debug parameter extraction and API calls

Speech and language issues

ProblemSymptomsSolution
Transcription accuracyIncorrect words in transcripts, missing words/phrases, poor performance with accentsSwitch to more accurate transcriber.
Intent recognitionAgent responds to wrong intent, fails to extract variables, workflow routing to wrong nodesMake system prompt / node prompt more specific; use clear enum values; adjust the temperature to ensure consistent outputs
Response qualityDifferent responses to identical inputs, agent forgets context, doesn’t follow instructionsReview system prompt / node prompt specificity; check model configuration; adjust temperature to achieve consistency

Debug steps for response quality:

  1. Review system prompt - Navigate to your assistant/workflow in the dashboard and check the system prompt specificity
  2. Check model configuration - Scroll down to Model section and verify:
    • You’re using an appropriate model (e.g., gpt-4o)
    • Max Tokens is sufficient for response length
    • Necessary tools are enabled and configured correctly
Response IssueSolution
Responses too longAdd “Keep responses under X words” to system prompt
Robotic speechSwitch to a different voice provider
Forgetting contextUse models with larger context windows
Wrong informationCheck tool outputs and knowledge base accuracy via Call Logs

Tool and workflow debugging

Problem TypeIssueSolution
Tool executionTools failing, HTTP errors, parameter issuesNavigate to Observe > Call Logs and check tool execution section, test tools individually at Tools > [Select Tool] > Test, validate configuration
Variable extractionVariables not extracted, wrong values, missing dataBe specific in variable descriptions, use distinct enum values, add validation prompts
Workflow logicWrong node routing, conditions not triggering, variables not passingUse Call Logs to trace conversation path, verify edge conditions are clear, check global node conflicts

Variable extraction details:

ProblemCauseSolution
Variables not extractedUnclear descriptionBe specific in variable descriptions: “Customer’s 10-digit phone number”
Wrong variable valuesAmbiguous enum optionsUse distinct enum values: “schedule”, “cancel”, “reschedule”
Missing required variablesUser didn’t provide infoAdd validation prompts to request missing data

Common error patterns

Error PatternLikely CauseQuick Fix
Agent misinterpreting speechSpeech recognition issueCheck transcriber model, add custom keyterms
Irrelevant responsesPoor prompt engineeringBe more specific in system prompt
Call drops immediatelyConfiguration errorCheck all required fields in assistant/workflow settings
Tool errorsAPI integration issueTest tools individually, verify endpoint URLs
Long silencesModel processing delayUse faster models or reduce response length

Getting help

When you’re stuck:

Before asking for help:

  • Include call ID and timestamp from Call Logs in your dashboard
  • Describe expected vs. actual behavior
  • Share relevant configuration (without API keys)
  • Include error messages from dashboard logs