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

Annotations already declare readOnlyHint and openWorldHint, but the description adds genuinely non-obvious behavior: the index only covers the most recent 10,000 articles and titles are currently absent in this index, which corrects a likely false expectation. It stops short of mentioning rate limits or pagination termination behavior, so it is strong rather than complete.

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 sentences, front-loaded with what is returned before the scope caveat and the alternative. Minor density in the nested parenthetical about titles, but no wasted sentences.

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 an output schema present, the description need not explain return shapes, yet it adds coverage limits, the title caveat, and an alternative route. For a one-parameter, read-only, paginated index tool this is complete.

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?

There is a single parameter with 100% schema description coverage ('Results page, 100 items per page'), so the schema already carries the semantics. The description's 'Returns a page' merely echoes pagination without adding format or bounds guidance, matching the baseline for high schema coverage.

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 a page of recent Reuters articles') and enumerates the returned fields (canonical URL, update time, lead image URL, conditional title). It also scopes the corpus ('most recent 10,000 articles') and names the sibling it is not (reuters_news), so an agent can distinguish it from reuters_article/reuters_news without opening schemas.

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?

Explicitly routes the agent: 'Use reuters_news to get fresh Reuters headlines with titles,' paired with the stated reason this tool lacks titles, giving a clear condition for choosing the alternative over this one.

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