Wixzel Voice

wixzel-voice-mcp

Wixzel Voice for AI agents. A Model Context Protocol server that lets Claude Code, claude.ai, Claude Desktop, Cursor, and any other MCP client create voice agents, connect a carrier, place calls, run campaigns, and read what it all cost, using the Wixzel Voice API.

Wixzel Voice: APIs for AI voice agents. One API key, one balance, every voice engine.

One tool per API operation, 56 in all, each annotated so a client knows which are read-only, which delete, and which spend money or make a real phone ring. Three prompts (quickstart, diagnose_call, spend_report) package the common workflows.

Published as wixzel-phone-mcp up to 0.3.0, while the product was briefly called Wixzel Phone. Those releases keep working: api.phone.wixzel.com and mcp.phone.wixzel.com keep serving.

Two ways to run it:

	Where	Auth
Hosted, https://mcp.voice.wixzel.com/mcp	Wixzel's servers	OAuth sign-in from the client, or a bearer key
Local, npx -y wixzel-voice-mcp	Your machine, stdio	WIXZEL_API_KEY in the environment

The console's AI clients page at voice.wixzel.com/connect generates every command below with a key filled in.

Claude Code

# hosted: sign in with your Wixzel account when Claude Code asks (/mcp → Authenticate)
claude mcp add --transport http wixzel-voice https://mcp.voice.wixzel.com/mcp

# local: a scoped key from the console
claude mcp add wixzel-voice -e WIXZEL_API_KEY=wv_live_... -- npx -y wixzel-voice-mcp

Or commit a .mcp.json so every collaborator gets it:

{
  "mcpServers": {
    "wixzel-voice": {
      "command": "npx",
      "args": ["-y", "wixzel-voice-mcp"],
      "env": { "WIXZEL_API_KEY": "${WIXZEL_API_KEY}" }
    }
  }
}

Then:

/mcp__wixzel-voice__quickstart

claude.ai and Claude Desktop

Settings → Connectors → Add custom connector → https://mcp.voice.wixzel.com/mcp → Connect. You sign in to the console, tick what the client may do, and it receives a scoped key of its own. Disconnect it from the console's AI clients page at any time.

Cursor, Windsurf, VS Code, others

Same shape as .mcp.json above: command npx, args ["-y", "wixzel-voice-mcp"], env WIXZEL_API_KEY. Clients that connect over HTTP but cannot do OAuth send the key as Authorization: Bearer wv_live_....

What the agent can do

Family	Tools
Engines	list_engines
Agents	list_agents get_agent create_agent update_agent delete_agent
Calls	place_call list_calls get_call get_call_transcript hangup_call delete_call
Callers	list_callers get_caller update_caller
Meetings	connect_meeting_integration get_meeting_integration delete_meeting_integration join_meeting list_meetings get_meeting leave_meeting
SIP trunks	list_sip_trunks get_sip_trunk create_sip_trunk update_sip_trunk delete_sip_trunk check_sip_trunk_status test_sip_trunk get_sip_trunk_logs
Phone numbers	list_phone_numbers get_phone_number create_phone_number update_phone_number delete_phone_number
Leads	list_leads get_lead create_lead update_lead delete_lead import_leads
Campaigns	list_campaigns get_campaign create_campaign start_campaign pause_campaign delete_campaign
Knowledge bases	list_knowledge_bases get_knowledge_base create_knowledge_base import_knowledge_base import_knowledge_file update_knowledge_base delete_knowledge_base list_knowledge_files add_knowledge_file get_knowledge_file delete_knowledge_file
MCP servers	list_mcp_servers get_mcp_server create_mcp_server update_mcp_server delete_mcp_server refresh_mcp_server connect_mcp_server_oauth
Tools	list_tools get_tool create_tool update_tool delete_tool test_tool
Voices	list_voices get_voice preview_voice create_voice_clone update_voice delete_voice
Appointments	list_appointments get_appointment create_appointment update_appointment delete_appointment
Billing & usage	get_balance list_ledger_entries create_topup get_usage_summary list_usage_events
API keys	list_api_keys create_api_key rotate_api_key revoke_api_key

Prompts: quickstart (connect a carrier, register a number, build an agent, place a first call), diagnose_call (why did call X fail), spend_report (what did this month cost, and where).

Resources: wixzel://guide (the operating guide the server also sends as its instructions) and wixzel://connection (base URL and whether the key is live or test; never the key itself).

How it keeps the agent honest

• Money is explicit. place_call, start_campaign, create_topup and create_voice_clone are annotated openWorldHint: true and their descriptions tell the model to confirm with the user first. Clients that gate on annotations will ask before running them.
• Idempotency is automatic. The two money paths require an Idempotency-Key; the server generates one per call and accepts an explicit idempotency_key for deliberate retries, so a network timeout never turns into two calls.
• Errors are actionable. Every failure returns the API's machine-readable code, the request_id, and a hint that says what to do: which scope is missing, that the balance is short, that a cursor was mangled.
• Rate limits are absorbed. A 429 is retried after Retry-After up to twice before the model sees it. Those requests are never charged.
• Scopes do the gating. The key decides what works. There is no admin scope, and a key cannot create one broader than itself.
• Secrets stay put. SIP passwords are write-only; API key secrets appear once, in the tool result, and nowhere else. The key this server runs with is never exposed through any tool or resource.

Running the hosted mode yourself

npx wixzel-voice-mcp --http 3939

Variable	Purpose
MCP_PORT	Port. Default 3939; --http <port> overrides.
MCP_BIND	Interface. Default 127.0.0.1; terminate TLS in front rather than binding wider.
MCP_PUBLIC_URL	The URL clients use, e.g. https://mcp.voice.wixzel.com/mcp. Advertised as the OAuth resource.
WIXZEL_API_BASE_URL	The API, which is also the OAuth authorization server. Default https://api.voice.wixzel.com.
WIXZEL_API_VERSION	Optional Wixzel-Version date pin.
WIXZEL_API_KEY	Stdio mode: the key. HTTP mode: a fallback for requests without a bearer, accepted only when MCP_PUBLIC_URL is a loopback address.

Each request's bearer becomes the API key for a fresh, throwaway MCP server; nothing is shared between requests. A request without a bearer gets a 401 with WWW-Authenticate: Bearer resource_metadata="…", and /.well-known/oauth-protected-resource names the API as the authorization server, which is how connectors discover sign-in on their own. GET /healthz reports liveness.

Development

The source is mirrored at wixzel-voice-sdks; it is developed in the private monorepo that also holds the API, so a change to an endpoint and the change to its tool land together.

npm install                # at the repo root
npm test -w apps/mcp       # offline: a fake API behind in-memory and HTTP transports, plus a spec-coverage check
npm run build -w apps/mcp
npm run inspect -w apps/mcp   # MCP Inspector against the built server

Tool schemas are hand-written zod. The spec-coverage test compares them against the API's OpenAPI document (docs/openapi.json) in both directions, so an endpoint added to the API fails the build here until it gets a tool.

Not for application code

This server is for AI agents. Application code should use the SDKs: wixzel-voice on npm and wixzel_voice on pub.dev.

License

MIT. Wixzel Voice itself is a hosted service; see voice.wixzel.com for terms.