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send16-mcp

by spruikco
OverviewSchemaSourceRelated ServersDiscussionsAdmin
JavaScript
Hybrid

send_email

Send transactional emails like receipts and OTPs. Provide HTML or plain text; from_email must be from a verified domain.

Instructions

Send a transactional email through Send16. Provide html, text, or both (text-only is fine for OTPs/receipts/alerts). from_email must belong to a domain that is verified in the workspace — call whoami for the account and list_domains to see which senders are allowed; a send from an unverified domain returns a clear error, not a silent failure. For a zero-setup first send, use from_email onboarding@send16.com — the sandbox sender delivers with no DNS, but only to your own account email.

Input Schema

TableJSON Schema
NameRequiredDescriptionDefault
toYesRecipient email address or array of addresses (max 50)
htmlNoHTML body content
textNoPlain text body content
apiKeyNoSend16 API key (overrides SEND16_API_KEY env var)
subjectYesEmail subject line
reply_toNoReply-to email address
templateNoTransactional template slug to use instead of inline content
from_nameNoSender display name (e.g. "Acme Co")
variablesNoTemplate variables for merge tags
from_emailNoSender email address (must be from a verified domain)

Schema Changelog

Changes observed during successful MCP inspections.

  1. First observedv0.5.7

TDQS

A4.3/5.0
Behavior4/5

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

Discloses that unverified domains return a clear error, not silent failure, and mentions the sandbox sender for zero-setup. With no annotations, this is transparent, but lacks details on rate limits or response format.

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?

Four sentences efficiently convey core information. Front-loaded with the purpose. Could be slightly more concise but no redundant content.

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

Completeness3/5

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

Covers sending behavior and parameter usage well, but lacks information on return values, error handling, and response structure. For 10 parameters, more completeness would help.

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

Parameters5/5

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

Schema covers 100% of parameters with descriptions. The description adds context on using html/text and domain verification for from_email, enhancing understanding beyond 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?

The description clearly states the tool sends transactional emails via Send16 and specifies the use of 'html', 'text', or both. It distinguishes from broadcast campaigns and other email-related tools.

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

Usage Guidelines4/5

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

Provides guidance on when to use (transactional emails) and mentions prerequisites like domain verification. References sibling tools 'whoami' and 'list_domains' for setup. Lacks explicit exclusion of marketing emails.

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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