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

Annotations already declare readOnlyHint=true and openWorldHint=true, so the safety profile is covered. The description adds freshness ('Current') and the public-section scope, but says nothing about result limits, ordering, or what the payload contains.

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 compact clause with the scoping constraint front-loaded and zero filler. Nothing could be removed without losing information.

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, read-only headline list with a full output schema and annotations, the description supplies what an agent needs to call it correctly, including the upstream dependency. Only minor gaps such as result window or pagination remain.

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 schema already enumerates every valid slug, so the baseline is 3. The description adds value beyond the schema by stating that the section must originate from metro_sections, establishing a cross-tool dependency the schema cannot express.

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 specific verb and resource ('headlines') plus the scope ('one public section'), which separates it from metro_article and metro_news. It does not explicitly contrast itself with the headline tools of other publishers (bbc_headlines, cnn_headlines), but the source prefix makes it unambiguous.

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?

The prerequisite 'section must come from metro_sections' is a concrete usage constraint that routes the agent to a sibling first. However, there is no guidance on when to choose this over metro_news or metro_article, so alternatives are left to inference.

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