getpoststack/mcp

Model Context Protocol server for the
PostStack Email API — an
EU-hosted, GDPR-compliant
email API for AI agents. Lets assistants
like Claude, Cursor, and Windsurf send transactional email, draft replies
from inbound threads, run deliverability checks, summarise broadcasts, and
more — through one curated tool surface.
117 tools, 5 prompts, and 5 resources, all surfaced over either the local
stdio bin or the hosted HTTP transport at https://api.poststack.dev/mcp.
Full MCP reference: poststack.dev/docs/mcp.
Quickstart
Hosted (Claude.ai connector, hosted agents)
Point any MCP client at:
Authenticate with your PostStack API key as a Bearer token. No local install required.
Claude Desktop (stdio)
Config file location:
- macOS: ~/Library/Application Support/Claude/claude_desktop_config.json
- Windows: %APPDATA%\Claude\claude_desktop_config.json
You can also generate the snippet with:
Claude Code
Cursor / VS Code
Same JSON shape as Claude Desktop, in the editor's MCP settings (Cursor:
~/.cursor/mcp.json, or .cursor/mcp.json in a project).
npx @poststack.dev/mcp --print-config cursor prints the whole file.
Environment variables
| Variable | Required | Description |
| --------------------- | -------- | ----------------------------------------------------------- |
| POSTSTACK_API_KEY | yes | PostStack API key (sk_live_… or sk_test_…) |
| POSTSTACK_BASE_URL | no | API origin (default https://api.poststack.dev) |
| POSTSTACK_MCP_TRACE | no | Set to 1 to emit per-tool-call NDJSON telemetry to stderr |
What the agent gets
The MCP server doesn't just mirror the REST API — it gives agents the context tools they need to make sensible decisions: spam-checking before sending, deliverability summaries before picking a from-address, engagement scores before re-engaging a contact.
Worked example: welcome email
The draft_welcome_email prompt walks an agent through:
1. get_contact_by_email — confirm the contact and capture properties
2. list_templates — pick a published welcome template
3. render_template — render with the contact's properties; surface any missing variables
4. suggest_from_address — pick a verified from-address based on existing mailboxes
5. preview_email — render + spam check + deliverability warnings in one round-trip
6. send_email — only if preview passed
Other prompts cover re-engagement, follow-up campaigns to non-clickers, broadcast summaries, and inbound triage.
Reference
Tools (117)
emails
- send_email — Send a single transactional email immediately, or schedule it for a future time.
- send_batch_emails — Send multiple emails in a single batch request (up to 100 per call).
- list_emails — List previously-sent emails with optional filters and pagination.
- get_email — Get full details and event timeline for a specific email by id.
- cancel_email — Cancel a scheduled email that has not yet entered the sending pipeline.
- reschedule_email — Reschedule a scheduled email to a new send time.
- lint_email — Run a Rspamd-backed spam pre-flight on a draft email and return the score, action, and per-rule symbols.
- preview_email — Render + lint + measure an email in one shot WITHOUT sending it.
email-validations
- validate_email — Check whether an email address is safe to send to BEFORE create_contact or send_email.
- validate_email_batch — Validate up to 100 email addresses in a single call. Same checks as validate_email per address.
contacts
- get_contact_activity — Get a contact's recent email-event timeline grouped by event type (sent / delivered / opened / clicked / bounced / complained / failed).
- get_engagement_summary — Get a single contact's engagement summary: segment + lifetime counts + open / click rates + last open / click + top tags.
- search_contacts — Search contacts with filters (segment, engagement, unsubscribed) and a fuzzy query across email/first_name/last_name. Adds a match_reason on each row indicating which field matched the query.
- create_contact — Create a new contact (person who can receive emails / broadcasts).
- list_contacts — List contacts with optional search and segment filtering.
- get_contact — Get full details of a contact by id.