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resend

Email Sending MCP

by resend

Update Template

update-template

Update template metadata such as name, subject, sender, HTML content, and variables by ID or alias. Changes require publishing to go live.

Instructions

Update template metadata by ID, alias, or Resend dashboard URL (name, subject, from, html, variables, etc.). After updating a published template, use publish-template again to make the changes live. To edit TipTap content, use compose-template instead.

Note on html/text fields: Setting html or text via this tool replaces any content previously set via compose-template. This switch is lossy — some content or formatting may be lost. Prefer compose-template for content changes. If the template was composed with TipTap content, ask the user before overwriting it with raw HTML.

Input Schema

TableJSON Schema
NameRequiredDescriptionDefault
idYesThe template ID, alias, or Resend dashboard URL (e.g. https://resend.com/templates/<id>)
fromNoNew sender email address.
htmlNoNew HTML content for the template. Email HTML requirements — follow all of these without exception: STRUCTURE - Always include <!DOCTYPE html>, <html>, <head>, <body> - Layout must be table-based: <table>, <tr>, <td> — never use <div> for layout - Outer wrapper table at width="100%", inner content table at max 600px wide - Every table must have cellpadding="0" cellspacing="0" border="0" CSS - All styles must be inline (style="...") — no <style> tag, no external stylesheets - No flexbox, no grid, no CSS variables, no CSS shorthand (use padding-top not padding) - font-family must always include web-safe fallbacks (Arial, Helvetica, Georgia, sans-serif) - Always set font-size, line-height, and color explicitly on every text element IMAGES - Always set width, height, border="0", display:block on every <img> - Use absolute URLs only — no relative paths - Always include alt text LINKS & BUTTONS - Never use <button> — use <a> styled as a button inside a <td> - No <video>, <form>, or <input> elements - No JavaScript of any kind OUTLOOK COMPATIBILITY - Use bgcolor attribute on <td> alongside CSS background-color - No CSS background-image (poor Outlook support) - Add <!--[if mso]> conditionals where needed for Outlook rendering META (in <head>) - <meta charset="UTF-8"> - <meta name="viewport" content="width=device-width, initial-scale=1.0"> - <meta http-equiv="X-UA-Compatible" content="IE=edge">
nameNoNew name for the template.
textNoNew plain text version of the message.
aliasNoNew alias for the template.
replyToNoNew Reply-to email address(es).
subjectNoNew default email subject.
variablesNoNew array of template variables (replaces existing variables).
Behavior4/5

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

With no annotations, the description carries full burden. It discloses that setting html/text replaces previous content from `compose-template` and is lossy. It also notes the need to republish for live changes. However, it does not mention authorization requirements, rate limits, or detailed response behavior. Still, key behavioral traits are covered.

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?

The description is long but well-structured with clear warnings and a detailed note on html/text. It front-loads the purpose and alternative. Could be slightly more concise, but every sentence adds value.

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

Completeness5/5

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

Given the complexity (9 parameters, 1 required, no output schema), the description covers behavioral aspects (lossy nature, need to republish), provides extensive HTML guidance, and references alternatives. It is complete enough for an AI agent to use correctly.

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 coverage is 100%, so a baseline of 3 would apply, but the description adds significant value: it includes extensive HTML requirements (structure, CSS, images, links, Outlook compatibility) for the `html` parameter, which goes far beyond the schema's minimal description. It also adds context about the lossy nature of html/text and the alternative `compose-template`.

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 uses specific verbs ('update template metadata') and resources ('by ID, alias, or Resend dashboard URL'), and explicitly distinguishes itself from sibling `compose-template` for TipTap content changes. This makes the tool's purpose clear and unambiguous.

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?

The description clearly states when to use this tool vs alternatives: it advises using `compose-template` for TipTap content, and instructs to re-publish via `publish-template` after updating a published template. It also warns about the lossy nature of html/text fields and suggests asking the user before overwriting.

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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