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

Annotations already declare readOnlyHint and openWorldHint, so safety and network scope are covered. The description still adds real behavioral context: the data comes from the public feed and returns headline items from the general stream rather than a curated or filtered set. It stops short of describing pagination or item count, but with annotations carrying the safety profile this is a solid contribution.

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 short sentences, front-loaded with what it fetches, then two precise sibling routing rules. Every clause earns its place with no redundancy.

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?

An output schema exists so return values need not be explained, and the description covers scope, source, and the alternative tools. Nothing an agent needs to invoke this zero-param tool correctly is missing.

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?

The tool takes zero parameters, so there is no parameter semantics for the description to supply; baseline is 4. The description's routing hints (e.g., returning article URLs usable with dailystaruk_article) add implicit output-shape value without needing parameter detail.

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 (fetch) and resource (Daily Star UK top stories) and pins the scope to the general top-story stream, explicitly contrasting it with dailystaruk_headlines (section-specific) and dailystaruk_article (single story body). An agent can select it without opening any 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?

Names both alternatives and the exact condition that selects each: use headlines for a section-specific list, use article with a returned URL for a story body. Nothing is left to inference.

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