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

With annotations already declaring readOnlyHint=false and destructiveHint=true, the description still adds real context: the tool returns two DNS records (CNAME and TXT) that the user must add at their DNS host before verification. It does not explain why a create operation is flagged destructive (e.g. does it block short-link creation until verified?) or whether repeat calls on an existing domain fail — a gap given idempotentHint=false.

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?

Three short sentences, front-loaded with the action and example, then the DNS/verify follow-up, then the rationale. Nothing is redundant and no sentence could be dropped without losing information.

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 usefully discloses the return payload (CNAME + TXT records) and the required next step. Missing only edge-case behavior — duplicate domains, failure modes, and the reason for the destructive flag — which an agent would want before calling.

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 description coverage is 0% for the single 'domain' parameter, so the description must carry the meaning — it does partly by showing the expected format ('links.example.com') and constraining it to the user's own subdomain. It leaves open whether a bare root domain is accepted and whether the subdomain prefix must be included.

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?

States a specific verb and resource ('Add a subdomain of the user's own ... for short links') and grounds it with a concrete example (links.example.com). An agent can immediately distinguish this from get_link_domain, list_link_domains, delete_link_domain, and verify_link_domain, the last of which is explicitly named as the follow-up step.

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 description sequences the workflow ('Returns two DNS records ... then verify the domain') and gives a rationale for using one's own subdomain rather than a shared one ('carriers filter those'). It stops short of explicit exclusions, e.g. when to use verify_link_domain vs check_verification, but the intended context is clear.

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