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

Annotations already state readOnlyHint, openWorldHint=false, idempotentHint and destructiveHint, so the safety profile is covered. The description still earns credit for adding real context beyond them: lowercase + NFC normalization per label, no full UTS #46 mapping, determinism, and hard limits (64 KB input, 1 s, 1 MB output). Score held at 3 rather than higher because the 'to or from this encoding' phrasing creates internal ambiguity about the direction of the transform.

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?

Content is front-loaded and the scoping sentence precedes the exclusion, which is good structure. But the text is duplicated ES/EN inside a single description and ends with a dangling meta-artifact ('[EN completo / full EN: inputSchema.description]') that repeats the schema description verbatim rather than adding anything.

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?

Output schema exists, so return values need not be explained. Combined with annotations plus the normalization, determinism and resource-limit disclosures, an agent has everything needed to call this correctly and to know it will not hit the network or mutate state.

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 the single 'domain' parameter already documents type and 253-char max, so the baseline is 3. The description adds meaning the schema lacks: that each label is lowercased and NFC-normalized before Punycode, which tells the agent mixed-case or decomposed-Unicode input is acceptable rather than an error.

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?

Names a concrete verb and resource ('Convierte un dominio internacionalizado a ASCII (Punycode, prefijo xn--)') and specifies the exact algorithm (RFC 3492) plus normalization steps, which distinguishes it cleanly from punycode-decode and from generic encoding tools.

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?

Explicit 'When' clause and an explicit 'Not for' clause naming the sibling punycode-decode, which is exactly the routing information an agent needs. However, the 'When' text says inputs must be converted 'to or from this encoding', which blurs the boundary the 'Not for' sentence just drew, since decoding is a different tool.

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