Mailcheer

Measured conclusion: Deep-tested. L2 outcome: tools_ok.

Email API + newsletters. 17 MCP tools. OAuth 2.1 PKCE or API key. EU-hosted (Hetzner + SES).

Add to your agent

Copy this into your MCP client config:

{
  "mcpServers": {
    "Mailcheer": {
      "url": "https://mailcheer.com/api/mcp",
      "transport": "streamable-http"
    }
  }
}

Measured tools (19)

• send_email destructive

  Sends a single (transactional) email to one or more addresses. The sender must belong to a verified domain of the workspace — call get_account to see which ones. An address suppressed for a bounce, a complaint or by hand fails the entire call, with its reason. An unsubscribed address still gets an individual email (a reply, an invoice, an appointment); a newsletter or a prospecting email must carry `unsubscribe_url`, and is then refused to an unsubscribed address. At most 50 addresses in all, to, cc and bcc together. Every address (to, cc, bcc) counts against the plan's monthly quota: past it, the call is refused (`quota_exceeded`) with the figures and the reset date — do not retry before that date. The email is sent immediately: this action cannot be undone.

  Parameters:

  • from (required) — string — Sending address on a verified domain. "Name <[email protected]>" format accepted.
  • to (required) — Recipient, or list of recipients.
  • subject (required) — string — Message subject.
  • html — string — HTML body.
  • text — string — Plain-text body. At least one of html or text is required.
  • verify — boolean — Verify recipients before sending: an address that cannot receive mail refuses the call (`undeliverable_recipient`) instead of bouncing. Recommended for prospecting.
  • replyTo — string — Reply-to address.
  • unsubscribe_url — string — One-click unsubscribe https address. Required for a newsletter or a prospecting email: it makes the send refused to an unsubscribed address. Leave it out for an individual email.

  Hints: read-only no · destructive yes · idempotent no · open-world no

• get_account read-only

  Returns the workspace this key grants access to, its scopes, plan, remaining emails this month (queued sends included), when the counter resets, billing status, member and domain limits, sending domains (verified or not) and registered senders. Call this FIRST: it tells you which address to send from before attempting anything.

  Hints: read-only yes · destructive no · idempotent yes · open-world no

• list_subscribers read-only

  Lists the workspace's subscribers, page by page. Use `cursor` with the `next_cursor` value from the response to get the next page. `status` filters on subscribed, pending, unsubscribed, bounced, or complained.

  Parameters:

  • q — string — Search by address or name.
  • limit — number — 1 to 100, 50 by default.
  • cursor — string — Next-page cursor.
  • status — string
  • updated_since — string — ISO 8601 date: only the records created or changed since then (status, name, fields, tags).

  Hints: read-only yes · destructive no · idempotent yes · open-world no

• add_subscriber

  Adds or updates a subscriber. By default the person enters as PENDING and receives a confirmation email: that is double opt-in, and it protects the workspace's sending reputation. `double_opt_in: false` subscribes directly and must only be used when consent was already collected elsewhere — never on your own initiative. A suppressed or unsubscribed address is refused. An address gets at most one confirmation every 2 minutes and 3 per 24 hours: do not retry in a loop, read `confirmation_not_sent_reason` and `confirmation_retry_at` in the response.

  Parameters:

  • email (required) — string
  • tags — array
  • lastName — string
  • firstName — string
  • double_opt_in — boolean — false = direct subscription without confirmation. Only request this on explicit instruction from the person.

  Hints: read-only no · destructive no · idempotent yes · open-world no

• remove_subscriber destructive

  Unsubscribes an address and adds it to the workspace's suppression list: no more campaigns, automations, or sends carrying `unsubscribe_url`. The record is not deleted — that is what prevents the address from coming back on the next file import. This action cannot be reversed via the API: only the person can re-subscribe.

  Parameters:

  • email (required) — string

  Hints: read-only no · destructive yes · idempotent no · open-world no

• update_subscriber

  Updates the first name (`first_name`), last name (`last_name`) and custom fields (`fields`, by technical key) of an existing subscriber. The email address cannot be changed: it is the identifier. Tags are managed with `tag_subscriber`. Unknown fields are rejected (400). The response contains the updated record and the `fields` keys that were ignored (`ignored_fields`).

  Parameters:

  • email (required) — string — The subscriber's email address (identifier).
  • fields — object — Custom field values keyed by their technical key.
  • last_name — string
  • first_name — string

  Hints: read-only no · destructive no · idempotent yes · open-world no

• list_tags read-only

  The workspace's tags, with how many subscribers carry each one (`subscribers`) and, among them, the active ones (`subscribed`). Read this before tagging: reuse an existing name rather than creating a near-duplicate.

  Hints: read-only yes · destructive no · idempotent yes · open-world no

• tag_subscriber

  Adds (`add`) and removes (`remove`) tags on ONE existing subscriber, and nothing else: no subscription, no confirmation email, no status touched. Prefer it to add_subscriber for changing tags: add_subscriber is a subscription and sends the confirmation again to a pending person. An unknown address is not created (404). The response says what really changed (`added`, `removed`).

  Parameters:

  • email (required) — string
  • add — array
  • remove — array

  Hints: read-only no · destructive no · idempotent yes · open-world no

• erase_subscriber destructive

  Erases a person from the workspace at THEIR request (right to erasure): record, name, fields, proof of consent, tags. Statistics of campaigns already sent do not move; the suppression list is not touched. To stop someone receiving anything, use remove_subscriber — not this one. IRREVERSIBLE: only use it on the explicit request of the person concerned, relayed by the user.

  Parameters:

  • email (required) — string

  Hints: read-only no · destructive yes · idempotent no · open-world no

• list_suppression read-only

  Suppressed addresses, with their reason: bounced, complained or manually suppressed (nothing goes to them), or unsubscribed (no more campaigns, automations, or sends carrying `unsubscribe_url`, but an individual email still reaches them). The `scope` field tells whether the address is suppressed for this workspace only or for the entire platform. No tool removes an address from this list: that action is done manually in the Mailcheer workspace, because it is the one that can suspend a sending capability.

  Parameters:

  • email — string — Look up a specific address.
  • limit — number
  • cursor — string

  Hints: read-only yes · destructive no · idempotent yes · open-world no

• add_suppression destructive

  Adds an address to the workspace's suppression list. By default (`manual`), it will receive nothing further, neither campaigns nor individual emails; with `unsubscribe`, only campaigns, automations, and sends carrying `unsubscribe_url` are refused to it. Use when someone requests no further contact outside the unsubscribe link.

  Parameters:

  • email (required) — string
  • reason — string

  Hints: read-only no · destructive yes · idempotent no · open-world no

• list_campaigns read-only

  The workspace's campaigns, from newest to oldest, with their status: draft, scheduled, sending, or sent.

  Parameters:

  • limit — number
  • cursor — string
  • status — string

  Hints: read-only yes · destructive no · idempotent yes · open-world no

• create_campaign

  Creates a DRAFT. Nothing is sent: you then need to call send_campaign, or send it from the Mailcheer workspace. Content is written in plain text in `text` — a blank line separates paragraphs, "#" at the start of a line makes a heading. Always have the draft reviewed before sending.

  Parameters:

  • name (required) — string — Internal name, visible only in the workspace.
  • from — string — Address of an already-registered sender. Defaults to the workspace sender.
  • kind — string — newsletter, offer, announcement… newsletter by default.
  • text — string — Plain-text content.
  • subject — string — Subject line seen by recipients.
  • preheader — string — Preview text shown after the subject in the inbox.

  Hints: read-only no · destructive no · idempotent no · open-world no

• update_campaign

  Edits a DRAFT: name, subject, preheader, kind, sender, content (`text`). Nothing is sent. Prefer it to create_campaign to rework a text: otherwise the old draft stays in the list. A scheduled, sending or sent campaign cannot be edited (409).

  Parameters:

  • id (required) — string
  • from — string
  • kind — string
  • name — string
  • text — string — The new content, in plain text: it replaces the old one.
  • subject — string
  • preheader — string

  Hints: read-only no · destructive no · idempotent yes · open-world no

• preview_campaign_send read-only

  Read-only: nothing is sent. Returns exactly what send_campaign would do right now — would it go out (and if not, why), and how many people would receive it. With `to`, reports address by address who is kept and who is excluded, with the reason (unsubscribed, bounced, complained, not in the list…). If the monthly quota is not enough, `would_send` is false, `blocked_code` is `quota_exceeded` and `blocked_details` gives the figures and the reset date. Call it BEFORE send_campaign, and give that number to the person when you ask them to confirm.

  Parameters:

  • id (required) — string — Campaign identifier.
  • to — array — Optional. The addresses to restrict the send to. Omitted = the campaign's whole audience.

  Hints: read-only yes · destructive no · idempotent yes · open-world no

• send_campaign destructive

  ⚠️ IRREVERSIBLE. Locks the recipient list and triggers sending to ALL active subscribers in the workspace — or, with `to`, only to the requested addresses that are active subscribers (never an unsubscribed or suppressed address). A sent email cannot be recalled. First call preview_campaign_send with the same parameters, then ask the person for explicit confirmation, telling them how many people will receive the message. Messages go out progressively; get_campaign_stats tracks progress.

  Parameters:

  • id (required) — string — Campaign identifier.
  • to — array — Optional. Restricts the send to these addresses. An empty list sends to nobody (refused); for the whole list, omit the field.

  Hints: read-only no · destructive yes · idempotent no · open-world no

• get_campaign_stats read-only

  Status and figures for a campaign: recipients, sent, delivered, opened, clicked, bounced, complained. Rates are calculated on delivered messages, not on recipients. Every rate comes twice: open_rate and click_rate include bots (security gateways, preloads), human_open_rate and human_click_rate set them aside — that is the figure to give the person when they ask how many read it.

  Parameters:

  • id (required) — string

  Hints: read-only yes · destructive no · idempotent yes · open-world no

• get_email read-only

  Status of an email sent via send_email: sent, delivered, bounced, or complained. Amazon's delivery callback arrives a few seconds to a few minutes after sending — a "sent" status right after the call is normal.

  Parameters:

  • id (required) — string

  Hints: read-only yes · destructive no · idempotent yes · open-world no

• verify_email read-only

  Verifies one or more addresses (up to 100) BEFORE writing to them, without sending anything: syntax, a domain that receives mail, a mailbox that already hard-bounced on Mailcheer, disposable or role mailboxes, and DNS signals of a dead mailbox. Each address gets a verdict: `invalid` (writing to it will bounce), `risky` (may bounce, or is not a person), `unknown` (DNS did not answer) or `valid` (nothing known against it — not a proof that the mailbox exists). Use it before prospecting, or before importing a list you did not collect yourself.

  Parameters:

  • emails (required) — array — The addresses to verify (1 to 100).

  Hints: read-only yes · destructive no · idempotent yes · open-world no

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