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

Adds concrete traits beyond the annotations: no network access, no stored state, deterministic output, and hard limits (64 KB JSON input, 1 s per call, 1 MB result). It also clarifies a real behavioral scope — only the domain is inspected, never the mailbox or the person. Some lines merely restate readOnlyHint/idempotentHint, which keeps it from a 5.

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?

Front-loaded with the core behavior, then organized under labeled clauses (Cuándo, No para, Efectos secundarios, Determinista, Límites), so it is easy to scan. It is somewhat long and the Spanish and English renderings duplicate content, which costs a point.

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 single-parameter lookup with an output schema, everything an agent needs is covered: input semantics, matching behavior including parent domains, negative scope versus the sibling, safety profile, determinism, and size/time limits. Return values are left to the output schema, as appropriate.

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 parameter already has an example, so the baseline is 3. The description still adds meaning by explaining that bare domains are accepted and that parent domains of the submitted domain are also resolved against the list, which changes how an agent should interpret subdomain 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?

States a specific verb and resource (check whether an email/domain or one of its parent domains is in a public university domain list) and adds what it returns (names the matching universities). It also draws a sharp boundary against the most confusable sibling, university-search, so the tool is identifiable without opening the 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?

Explicit 'Cuándo' clause defines the trigger (an email or domain presented as academic needs verification against the public list) and the 'No para' clause names the alternative tool and its distinguishing condition (searching ~10,000 universities by name words). When-to-use, when-not, and the alternative are all present.

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