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

Annotations already flag destructiveHint=true and openWorldHint=true, yet the description adds substantial detail beyond them: remove kills open connections before responding and requires the agent to delete DNS records at the external provider, verify reports whether the name currently points at Runtime, and add requires a funded top-up. These side effects and prerequisites are exactly the kind of context an agent cannot infer from annotations.

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?

One front-loaded purpose sentence followed by compact per-action clauses; every sentence carries information. The signature-style notation (add(...), verify(...)) is terse but readable, though the run-on quality of some clauses slightly reduces scanability.

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, the description does the work of describing returns: DNS records for add, activation status plus pointing state for verify, state and records per domain for list. It covers all four actions adequately, with only minor gaps (e.g. possible domain states, whether list paginates).

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 only 50% (hostname and action undocumented), but the description compensates by showing the per-action signatures — add(hostname, sandboxId, port), verify(hostname), remove(hostname) — which tells the agent which parameters apply to which action. It adds real meaning over the bare enum, though it doesn't clarify the shape of 'list' input.

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 opening sentence names a specific verb and resource — serving a sandbox port at a custom hostname with automatic HTTPS — and the per-action breakdown (add/verify/list/remove) makes each capability explicit. No sibling tool covers custom-domain mapping, so the resource itself is disambiguating.

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 lays out the workflow conditions: add returns records to configure, verify must be run and only activates when the TXT matches, remove stops serving. The prerequisite 'Needs a kept top-up' is stated. It does not name alternative tools (e.g. previews/ports) or say when not to use this one, but the resource is niche enough that the forward path is clear.

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