Retell AI MCP server and Dome

1. 01

   Add the Retell MCP server

   Dome holds the Retell API key and sends it as a Bearer token. Agents never see it.

   $ dome tools add --name retell \
     --url https://mcp.retellai.com \
     --auth-method api-key \
     --credential-type shared \
     --authorization "Bearer $RETELL_API_KEY" \
     --gateway voice-gateway

2. 02

   Sync the catalog

   Sync lists Retell's three tools: list_api_endpoints, get_api_endpoint_schema, and invoke_api_endpoint.

   $ dome tools catalog sync retell

3. 03

   Apply the rules

   The endpoint list is scoped to appointment-confirmer. Simulate a batch call to see it refused, then deploy.

   $ dome rules apply retell-calls.cedar \
     --agent appointment-confirmer --name retell-calls

4. 04

   Cap the agent's calls

   A hundred calls a day for appointment-confirmer. Every tool call counts, reads included.

   $ dome quotas set --subject agent --agent appointment-confirmer \
     --dimension tool --unit calls --limit 100 --window daily

Commands and rules tested against a Dome workspace on October 1, 2026. For anything about Retell AI itself, see Retell AI's documentation.

permit (principal, action == Dome::Action::"mcp:call", resource is Dome::MCPTool)
when { resource.connection_name == "retell" };
 
forbid (principal, action == Dome::Action::"mcp:call", resource is Dome::MCPTool)
when {
  resource.connection_name == "retell" &&
  resource.tool_name == "invoke_api_endpoint"
}
unless {
  resource has arguments &&
  resource.arguments has endpoint &&
  (["listCalls", "getCall", "listAgents", "getAgent"].contains(resource.arguments.endpoint) ||
   (resource.arguments.endpoint == "createPhoneCall" &&
    resource.arguments has arguments &&
    resource.arguments.arguments has requestBody &&
    resource.arguments.arguments.requestBody has to_number &&
    resource.arguments.arguments.requestBody has override_agent_id &&
    resource.arguments.arguments.requestBody.to_number like "+1*" &&
    resource.arguments.arguments.requestBody.override_agent_id == "agent_appointment_confirm" &&
    !(resource.arguments.arguments.requestBody has agent_override)))
};