Sendsets MCP server

Sendsets: the cold email API for AI agents

Sendsets gives AI agents a programmable way to run cold email. An agent (Claude Code, Codex, Cursor, Gemini CLI, ChatGPT, or your own code) can connect sending mailboxes, warm them up, build and launch outbound campaigns, add leads, and read and answer replies through an MCP server, a CLI, or a REST API instead of a sales dashboard.

This repository is the public, agent-facing home of Sendsets:

Sign up at app.sendsetsapi.com. Free for up to 10 mailboxes.

What an agent can do with it

The MCP server and the REST API expose the same service-layer tools. What a credential can see is limited by the scopes it was granted.

• Campaigns: create a draft, add and edit sequence steps, pick sender mailboxes, view leads, logs and stats, start and stop
• Leads and contacts: add, search, tag, bulk edit, read timelines and sent mail, manage segments
• Mailboxes: list and inspect connected mailboxes, adjust limits, toggle warmup, set tracking domains, check warmup standing
• Inbox and replies: list and read threads, draft and send replies, label, snooze, cancel scheduled sends
• Runs: durable, idempotent, preflighted campaign runs (createrun, getrun, listruns, cancelrun)
• Suppressions, analytics, webhooks: manage the do-not-contact list, read dashboard analytics, manage signed webhooks

Send-class tools (startcampaign, composeemail, sendreply, and an autonomous createrun) go through a credential-bound policy. A call returns executed, awaiting_approval (a person approves it in the dashboard within 30 minutes), or blocked. Approval can never override a missing opt-out, a suppression, or a mailbox health check.

Connect the MCP server

The server advertises OAuth 2.1 protected-resource metadata (RFC 9728) and supports dynamic client registration, so MCP clients that speak OAuth sign you in through the browser with no key to paste. A static ssk API key from the dashboard works too, as Authorization: Bearer ssk....

Claude Code

claude mcp add --transport http sendsets https://api.sendsetsapi.com/v1/mcp

Or install the plugin, which adds the MCP server and the skills together:

/plugin marketplace add AddisonHoff/sendsets
/plugin install sendsets@sendsets

Claude (claude.ai and Claude Desktop): Settings > Connectors > Add custom connector, URL https://api.sendsetsapi.com/v1/mcp.

Codex

codex plugin marketplace add AddisonHoff/sendsets     # MCP server + skills as a plugin

or just the MCP server:

codex mcp add sendsets --url https://api.sendsetsapi.com/v1/mcp
codex mcp login sendsets

Cursor (~/.cursor/mcp.json)

{
  "mcpServers": {
    "sendsets": { "url": "https://api.sendsetsapi.com/v1/mcp" }
  }
}

Shortened. The full README is on GitHub.