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

Annotations already declare readOnly, idempotent, closed-world and non-destructive, so the safety profile is covered. The description adds real behavioral detail beyond that: what fields are included (validity dates, official source domain, date last checked) and the notable edge case that closed or unconfirmed guides return only their status rather than an error.

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?

A single front-loaded sentence that leads with the verb and resource before enumerating contents; nothing is padding, though the field list partially duplicates what the output schema already declares.

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 annotations covering the safety profile, a full output schema, and a 100%-covered input schema, the description supplies everything else an agent needs, including the degraded-response case for closed guides.

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%, including an enumerated lang parameter with an explicit default rule, so the schema already carries parameter meaning. The description adds nothing about slug format or language selection beyond echoing 'by slug', which is the baseline-3 situation.

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 ('Returns one guide by slug') and enumerates exactly what comes back, which inherently separates it from search_guides (many results) and about_guia (meta information). An agent knows precisely what this tool produces 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?

Usage is only implied: the slug parameter notes it comes 'from search_guides', so the search-then-fetch flow is inferable, but the description itself never says when to call this instead of search_guides or about_guia, nor any prerequisites.

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