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

Annotations already declare readOnlyHint=true, idempotentHint=true, destructiveHint=false and openWorldHint=false, so the safety profile is covered. The description still adds real value the annotations cannot convey: it explains the tool "opens nothing by itself" and returns screen/button/field level guidance, which prevents an agent from assuming a send actually occurred. The closing paragraph about Mailjet's REST API and read-only official MCP server is background trivia that adds no operational guidance for invoking this tool.

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

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

Front-loaded: the first clause states what the tool is and the very next clause corrects the likely misreading ("opens nothing by itself"). Every sentence about the tool's own behavior earns its place.

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

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

With no output schema and no parameters, the description carries the burden of explaining what comes back, and it does specify a step-by-step guide covering screens, buttons and fields. It is somewhat less complete on the shape/limits of that returned guidance, but sufficient for a zero-arg guidance tool.

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

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

The tool takes zero parameters, so per the baseline the schema carries no semantics to compensate for. The description correctly implies no input is required and instead frames the interaction as a retrieve-then-act flow via browser tools.

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

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

The description names a concrete verb+resource ("Send campaign in the user's own Mailjet account") and then clarifies the real mechanic: it returns step-by-step instructions rather than acting. It distinguishes itself from the browser siblings by handing off to cotlet_browser_* tools, but never contrasts itself with close siblings like mailjet_schedule_campaign or mailjet_get_campaign_report, so an agent must infer the split.

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

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

It gives a usable follow-on workflow ("then do it with the cotlet_browser_* tools in the user's Mailjet Cloud Browser"), which implies when to reach for this tool. However, it offers no explicit when-not condition and no guidance on choosing between sending now versus scheduling, even though mailjet_schedule_campaign is a live alternative.

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