Vapi Voice Agent

Vapi Voice Agent Skill

This skill enables Claude to manage voice calls through the Vapi platform using the Vapi MCP Server.

Prerequisites

The Vapi MCP server must be configured in your Claude Code (or Claude Desktop) MCP settings.

Claude Desktop Configuration

Add this to your claude_desktop_config.json:

{
  "mcpServers": {
    "vapi-mcp": {
      "command": "npx",
      "args": [
        "mcp-remote",
        "https://mcp.vapi.ai/mcp",
        "--header",
        "Authorization: Bearer ${VAPI_TOKEN}"
      ],
      "env": {
        "VAPI_TOKEN": "YOUR_VAPI_API_KEY"
      }
    }
  }
}

Claude Code Configuration

claude mcp add vapi-mcp \
  --transport sse \
  --url "https://mcp.vapi.ai/sse" \
  --header "Authorization: Bearer YOUR_VAPI_API_KEY"

Get your API key from: https://dashboard.vapi.ai/org/api-keys

Available MCP Tools

The Vapi MCP server exposes these tools:

Capabilities

1. Make an Outbound Call

Use list_assistants to find the right assistant, list_phone_numbers to find the caller ID, then create_call to initiate.

Workflow:

1. Call list_assistants → pick the appropriate assistant (by name or purpose)
2. Call list_phone_numbers → pick the phone number to call from
3. Call create_call with:
   • assistantId: the chosen assistant's ID
   • phoneNumberId: the Vapi phone number ID (caller ID)
   • customer.number: the destination phone number in E.164 format (e.g. +15551234567)
   • scheduledAt (optional): ISO 8601 datetime to schedule the call for later

Example prompt: "Call Jeremy at +1-555-123-4567 using the customer support assistant."

2. Query Recent Calls (Last Hour)

Use list_calls to retrieve calls from a specific time window. The MCP tool supports filtering by createdAtGe (created at ≥) and createdAtLe (created at ≤) parameters.

Workflow:

1. Call list_calls with time filter parameters to get calls from the last hour (or any window)
   • Use createdAtGe with an ISO 8601 timestamp for "1 hour ago"
   • Optionally filter by assistantId to narrow results
2. For each call returned, call get_call with the call's id to retrieve full details including:
   • transcript — the full text transcript of the conversation
   • messages — array of individual utterances with role, message, and timestamps
   • analysis.summary — AI-generated summary (if analysis plan is configured)
   • status — call status (queued, ringing, in-progress, forwarding, ended)
   • endedReason — why the call ended
   • startedAt / endedAt — call timing
   • cost — call cost breakdown
   • type — inboundPhoneCall, outboundPhoneCall, or webCall

Example prompt: "Show me all incoming calls from the last hour and summarize what was discussed."

3. Summarize Call Transcriptions

After retrieving calls via list_calls + get_call, summarize the transcriptions.

Workflow:

1. Retrieve calls as in capability #2
2. For each call with a transcript, extract:
   • Call type (inbound/outbound)
   • Caller/callee number
   • Duration (from startedAt and endedAt)
   • The transcript field (full conversation text)
   • The analysis.summary field if available
3. Present a summary including:
   • Number of calls in the time window
   • For each call: who called, when, duration, and a concise summary of the conversation
   • Any notable patterns or action items mentioned

Example prompt: "Summarize all calls from the last 2 hours — group by inbound vs outbound."

Response Format

When presenting call summaries, use this structure:

## Call Summary — [Time Window]

**Total calls:** X (Y inbound, Z outbound)

### Call 1 — [Inbound/Outbound] at [time]
- **From/To:** [phone number]
- **Assistant:** [assistant name]
- **Duration:** [X minutes]
- **Summary:** [concise summary of the conversation]
- **Action items:** [if any were mentioned]

### Call 2 — ...

Tips

• Phone numbers must be in E.164 format: +15551234567 (with country code, no spaces/dashes)
• The analysis.summary field is only populated if the assistant has an analysis plan configured — if missing, summarize from the raw transcript or messages array
• The list_calls tool returns calls in reverse chronological order by default
• Call transcripts may be empty for very short or failed calls — check status and endedReason
• Use scheduledAt on create_call to schedule calls for a future time

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