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 fully covered without the description. The description adds the useful context that the calls it suggests require no auth and that a signed-create path exists locally, but it says nothing about the response shape or size. With annotations carrying the burden, this is adequate but not rich.

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?

A single sentence with three tightly packed clauses, front-loaded with the learning purpose and ending with the actionable pointer. No filler or redundancy.

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?

For a parameterless onboarding tool with no output schema, the description is nearly sufficient: it tells the agent what it will get and what it can try. The one gap is that it does not describe the form of the returned guidance (text overview vs. links), which an agent might want when planning follow-up calls.

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 and the schema is fully described, so there is no parameter information the description needs to compensate for. Baseline of 4 applies, with no misleading parameter claims.

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 concrete outputs: an explanation of what the hosted Voidmail server does, three no-auth example calls, and a pointer to the local signed-create path. That separates it from siblings like voidmail_send_once or voidmail_read_email, which are specific operations rather than an entry point. It never explicitly says the tool returns onboarding/documentation content, which keeps it short of a 5.

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?

The onboarding framing ('Start using Voidmail') plus 'try three no-auth calls' and 'find the local signed-create path' gives clear context for when to call it (first, before the auth-requiring siblings). There is no explicit when-not-to-use or naming of which sibling to use next, so routing is implied rather than stated.

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