zend.shzend.sh
Native interfaces
Pick the interface that fits your workflow. Every surface exposes the full capability of the platform — accounts, campaigns, leads, analytics, webhooks, and warmup status.
REST API
80+ endpoints. Bearer auth. IETF rate-limit headers. Consistent error format. Sandbox mode via zk_test_* keys.
TypeScript SDK
Full type definitions. Namespaced resources. Published to npm as zend-sh.
Python SDK
Sync and async clients. Pydantic v2 models. Published to PyPI as zend-sh.
CLI
zend commands for every operation. JSON output. Pipe to jq. Script your workflows from the terminal.
MCP Server
Streamable HTTP transport. AI agents create campaigns, manage leads, and monitor deliverability conversationally.
Webhooks
HMAC-SHA256 signed. Retry with exponential backoff. Filter by event type. Real-time delivery to your endpoint.
Your existing stack
Webhook events, the REST API, and the SDK integrate cold email into the tools you already use — CRMs, lead sources, workflow automation, AI agents, communication tools, and analytics platforms.
CRMs
HubSpot, Salesforce, Attio, Close, Pipedrive. Webhook events push reply intents, lead status changes, and campaign completions in real time.
Lead sources
Apollo, Clay, waterfall.sh, LinkedIn Sales Nav. Import leads via CSV or API with custom fields. Deduplicate against suppression list automatically.
Workflow automation
Zapier, n8n, Make, Tray.io. Trigger campaigns from form fills, CRM events, or schedules. Pause on reply. Route by intent.
AI agents
Claude, GPT-4, and custom agents via MCP. AI agents create campaigns, add leads, and monitor deliverability conversationally.
Communication
Slack, Email, Discord. Webhook alerts for replies, bounces, and health warnings. Never miss an interested lead.
Analytics
Looker, Metabase, custom dashboards. Events API with date range filtering. Export to any BI tool via JSON. Per-campaign and per-account breakdowns.
Bearer token auth — include your API key as Authorization: Bearer zk_live_... for production or zk_test_... for sandbox. Keys are scoped to your team and can be rotated from the dashboard. The sandbox environment uses test keys and does not send real emails.
The MCP server exposes 58 tools covering accounts, campaigns, leads, analytics, warmup, webhooks, and suppression. It uses streamable HTTP transport so AI agents (Claude, GPT-4, and custom agents) can interact with zend.sh conversationally — creating campaigns, checking deliverability, and processing replies without writing API calls manually.