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 the scoping behavior, that results come from the general top-story stream (not a filtered set), which is real context beyond the annotations. It stops short of mentioning result ordering, freshness, or result count.

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 tight sentences, front-loaded with the fetch purpose, then the two alternative tools. Nothing is redundant given the output schema already documents the return shape, and each sentence routes the agent somewhere useful.

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 and annotations covering safety, the description needs only to convey purpose, scope, and sibling routing, all of which are present. Nothing an agent needs to call this 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 nothing to disambiguate; baseline is 4. The description appropriately avoids inventing parameter guidance for a parameterless call.

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 (fetch Financial Times stories) and names exactly what is returned: title, canonical URL, publication time. It explicitly distinguishes itself from ft_headlines (section-specific) and ft_article (single story body), so an agent can place it among siblings 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?

Gives clear when-to-use conditions and names both alternatives with their selecting conditions: use ft_headlines for a section-specific list, and use ft_article with a returned URL when one story's body is needed. This is explicit routing rather than implied usage.

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