Hellio Messaging Server

A Model Context Protocol server that exposes the Hellio Messaging API to any MCP-capable AI client (Claude Desktop, Claude Code, Cursor, and others).

It maps every Hellio API operation to a tool: SMS, OTP, voice, HLR lookup, email verification, balance and pricing, webhooks, and the full USSD suite (apps, extensions, sessions, sandbox simulation). 28 tools in total.

Requirements

• Node.js 18 or newer
• A Hellio Sanctum personal access token. Its scopes decide which tools can succeed.

Build

cd mcp-server
npm install
npm run build

This compiles to dist/. The entrypoint is dist/index.js.

Configuration

The server reads two environment variables:

Variable	Required	Default	Notes
HELLIO_API_TOKEN	yes	-	Your Sanctum bearer token.
HELLIO_API_BASE_URL	no	https://api.helliomessaging.com	Override to point at staging or local.

Copy .env.example to .env for local testing, or pass the variables through your MCP client config (below).

Connect it to a client

Claude Desktop

Edit claude_desktop_config.json (Settings, Developer, Edit Config) and add:

{
  "mcpServers": {
    "hellio": {
      "command": "node",
      "args": ["/absolute/path/to/hellio-v2/mcp-server/dist/index.js"],
      "env": {
        "HELLIO_API_TOKEN": "your-token-here"
      }
    }
  }
}

Restart Claude Desktop. The Hellio tools appear under the tools menu.

Claude Code

claude mcp add hellio \
  --env HELLIO_API_TOKEN=your-token-here \
  -- node /absolute/path/to/hellio-v2/mcp-server/dist/index.js

Try it

Use the MCP Inspector to click through the tools without a full client:

npm run inspect

Then set HELLIO_API_TOKEN in the Inspector's environment panel and call, for example, hellio_get_balance.

Tools

Read-only (safe to call freely):

• hellio_get_balance, hellio_get_pricing
• hellio_list_messages, hellio_get_message, hellio_list_campaigns, hellio_get_campaign
• hellio_list_webhooks
• hellio_ussd_get_pricing, hellio_ussd_check_extension_availability
• hellio_ussd_list_apps, hellio_ussd_list_extensions
• hellio_ussd_list_sessions, hellio_ussd_get_session

Writes that charge your account (each description begins with "Deducts from your"):

• hellio_send_sms, hellio_send_otp, hellio_send_voice
• hellio_lookup_numbers, hellio_verify_email
• hellio_ussd_rent_extension

Other writes:

• hellio_verify_otp, hellio_create_webhook
• hellio_ussd_create_app, hellio_ussd_update_app, hellio_ussd_delete_app
• hellio_ussd_switch_app_mode, hellio_ussd_rotate_app_secret, hellio_ussd_release_extension
• hellio_ussd_simulate

Safety notes

• Billable sends attach an Idempotency-Key automatically, so a retried tool call replays the original response instead of double-charging.
• Every tool carries MCP annotations (readOnlyHint, destructiveHint) so clients can gate or confirm the risky ones.
• Which tools succeed depends on the token's scopes. A 403 or "insufficient scope" error means the token lacks that ability, not that the tool is broken.

Project layout

mcp-server/
  src/
    index.ts        server bootstrap, stdio transport
    config.ts       env loading
    client.ts       authenticated HTTP wrapper + idempotency
    format.ts       tool result helpers
    tools/          one file per API domain
  dist/             compiled output (generated)

To add a tool, add it to the matching file in src/tools/ and rebuild.