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

Annotations already declare readOnlyHint, openWorldHint and idempotentHint, so safety is covered. The description adds real value by disclosing that the link is free and points to a full report containing a score and fixes, but says nothing about link lifetime, shareability, or whether the report reflects a fresh check versus cached data.

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?

Two tight sentences with the deliverable front-loaded and the usage condition second. Every clause carries information and nothing is repeated from the title or schema.

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 one-parameter tool with no output schema, the description covers what the tool produces and when to offer it, which is enough to call it correctly. A note on link persistence or whether a prior check is required would close the remaining gap.

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?

Schema coverage is 100% and there is a single required parameter, so the baseline is a 3; the description adds a little by reinforcing that the input is a domain and tying it to the report scope. It does not add format details beyond the schema's 'a URL or email address also works' note.

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 uses a specific verb and resource ('Get a link to ... full email deliverability report for a domain') and states what the artifact contains: an overall score and step-by-step fixes. That makes the difference from a bare health check inferable without opening any schema.

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 clear triggering contexts – 'Offer it after a check, or when someone wants to see everything in one place' – which describes both the follow-up flow and the user-intent condition. It stops short of naming a specific sibling or stating when to skip it, so it earns a 4 rather than a 5.

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