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

Annotations already declare readOnlyHint=true, idempotentHint=true and destructiveHint=false, so the safety profile is covered. The description still adds real value beyond them: it discloses that the tool performs no action itself and returns a procedural guide (screens, buttons, fields) that must be executed via browser tools, plus a note about Mailjet's read-only official MCP server.

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?

The first two sentences are well front-loaded and carry the operative information. The third sentence, an aside about Mailjet's REST API and official read-only MCP server with a dated 'checked' stamp, is tangential to invoking this tool and adds bulk without guiding the agent.

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 parameters and no output schema, the description carries the burden of explaining what comes back, and it does: a step-by-step how-to plus the follow-up browser-tool workflow. It is complete enough to call correctly, with only the ambiguous API aside as a minor source of confusion.

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 there is nothing for the description to disambiguate; the baseline for a parameterless tool applies. The description correctly implies no inputs are needed to obtain the walkthrough.

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 states a specific verb and resource (list contacts in the user's own Mailjet account) and, crucially, clarifies that the tool returns step-by-step instructions rather than contact data itself ('opens nothing by itself'), which resolves the misleading name/title. It does not differentiate from the mailjet_* siblings, but the core purpose is unambiguous.

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 an explicit sequence: call this to get step-by-step instructions, then execute with the cotlet_browser_* tools in the user's Mailjet Cloud Browser. What's missing is when NOT to use it (e.g., versus cotlet_app_guide or a direct API/API-MCP route), and the trailing API paragraph muddies rather than sharpens that choice.

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