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Mailcheer

by com.mailcheer
OverviewDiscussionsAdmin

Send an email

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.

Input Schema

NameRequiredDescriptionDefault
toYesRecipient, or list of recipients.
fromYesSending address on a verified domain. "Name <address@domain.com>" format accepted.
htmlNoHTML body.
textNoPlain-text body. At least one of html or text is required.
verifyNoVerify recipients before sending: an address that cannot receive mail refuses the call (`undeliverable_recipient`) instead of bouncing. Recommended for prospecting.
replyToNoReply-to address.
subjectYesMessage subject.
unsubscribe_urlNoOne-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.

Schema Changelog

Changes observed during successful MCP inspections.

  1. Changed1 schema field changed
    • addedInput schema / properties / verify
      Added value: +{
+  "description": "Verify recipients before sending: an address that cannot receive mail refuses the call (`undeliverable_recipient`) instead of bouncing. Recommended for prospecting.",
+  "type": "boolean"
+}
  2. Changed1 schema field changed
    • addedInput schema / properties / unsubscribe_url
      Added value: +{
+  "description": "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.",
+  "type": "string"
+}
  3. First observed

TDQS

A4.7/5.0
Behavior5/5

Does the description disclose side effects, auth requirements, rate limits, or destructive behavior?

Annotations already declare destructiveHint=true and idempotentHint=false, and the description compounds that with behavior annotations don't carry: the send is immediate and irreversible, a suppressed address fails the entire call with its reason, quota exhaustion returns quota_exceeded with figures and a reset date, and the 50-address ceiling. This is exactly the extra context the annotations cannot supply.

Agents need to know what a tool does to the world before calling it. Descriptions should go beyond structured annotations to explain consequences.

Conciseness4/5

Is the description appropriately sized, front-loaded, and free of redundancy?

Front-loaded with the core action, then structured as successive constraints, each sentence carrying distinct operational information. It is dense and long, and the to/cc/bcc reference slightly muddies the parameter story, but almost nothing is filler.

Shorter descriptions cost fewer tokens and are easier for agents to parse. Every sentence should earn its place.

Completeness4/5

Given the tool's complexity, does the description cover enough for an agent to succeed on first attempt?

For a destructive, non-idempotent, no-output-schema tool, this covers the failure modes, quota accounting, suppression semantics, and irreversibility that an agent needs. The only gap is the mismatch between the described cc/bcc recipients and the schema, which exposes exactly three recipient fields.

Complex tools with many parameters or behaviors need more documentation. Simple tools need less. This dimension scales expectations accordingly.

Parameters4/5

Does the description clarify parameter syntax, constraints, interactions, or defaults beyond what the schema provides?

Schema coverage is 100%, so the baseline is 3, but the description adds cross-parameter meaning the schema lacks: every to/cc/bcc address consumes the monthly quota, unsubscribe_url changes the send's eligibility rules, and verify is recommended for prospecting. Minor deduction because it references cc and bcc, which are absent from the input schema.

Input schemas describe structure but not intent. Descriptions should explain non-obvious parameter relationships and valid value ranges.

Purpose5/5

Does the description clearly state what the tool does and how it differs from similar tools?

"Sends a single (transactional) email to one or more addresses" gives a precise verb, resource, and scope. The "single/transactional" framing implicitly separates it from the sibling send_campaign, and the distinction is reinforced later by the newsletter-vs-individual-email rules.

Agents choose between tools based on descriptions. A clear purpose with a specific verb and resource helps agents select the right tool.

Usage Guidelines5/5

Does the description explain when to use this tool, when not to, or what alternatives exist?

Explicitly routes the agent to get_account to discover verified domains, states when unsubscribe_url is mandatory (newsletter/prospecting) versus when to omit it (reply, invoice, appointment), and describes what to do on quota_exceeded (do not retry before the reset date). This is when-to-use, when-not-to-use, and alternative-tool guidance all in one.

Agents often have multiple tools that could apply. Explicit usage guidance like "use X instead of Y when Z" prevents misuse.

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