Mailosaur MCP

mailosaur_messages_generate_previews

Generate screenshots of an email rendered in selected email clients to verify visual appearance and layout.

Instructions

Generate screenshots of an email rendered in selected email clients.

Tool call template

Replace each placeholder with a value matching the input schema. Only required parameters are included; add optional parameters as needed.

{
  "id": 1,
  "jsonrpc": "2.0",
  "method": "tools/call",
  "params": {
    "arguments": {
      "messageId": "<messageId>",
      "previews": "<previews>"
    },
    "name": "mailosaur_messages_generate_previews"
  }
}

Input Schema

Name	Required	Description	Default
`messageId`	Yes
`previews`	Yes

Schema Changelog

Changes observed during successful MCP inspections.

First observedv0.1.0May 18, 2026

TDQS

C2.9/5.0

Behavior2/5

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

No annotations exist, so the description must convey behavioral traits. It only states 'Generate screenshots' without disclosing whether it is read-only, if it modifies state, or any caveats. Minimal behavioral transparency.

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

Conciseness5/5

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

The description is a single, well-formed sentence with no wasted words. It front-loads the core purpose and is appropriately concise.

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

Completeness2/5

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

Given the complexity (two parameters, nested objects) and lack of output schema or annotations, the description is too sparse. It fails to explain the context of messageId, previews array behavior, or valid client values, leaving the agent with insufficient information.

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

Parameters1/5

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

Schema description coverage is 0%, and the description does not explain any parameters (e.g., what messageId refers to, valid emailClient values, or the effect of disableImages). The agent receives no semantic help beyond the 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 action ('Generate screenshots') and resource ('an email rendered in selected email clients'), distinguishing it from sibling tools like mailosaur_files_get_preview and mailosaur_previews_list_email_clients.

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

Usage Guidelines2/5

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

No guidance is provided on when to use this tool versus alternatives (e.g., mailosaur_files_get_preview for existing previews). The description lacks when-to-use or when-not-to-use instructions.

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

Deploy Server