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

Annotations already declare readOnlyHint, idempotentHint, and openWorldHint, so the safety profile is covered. The description adds that results include summaries plus canonical URLs, which is mildly useful context, but with an output schema present it adds little behavioral disclosure beyond the structured data.

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 what, then usage intents, then return shape and categories. Nothing is padding, though the return-shape sentence is partly redundant given an output schema exists.

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 safety, an output schema covering returns, and full parameter documentation, the description only needs to add routing and category semantics, which it does. It is complete enough to call correctly, lacking only explicit alternative-tool guidance.

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% so the baseline is 3, but the description adds real value: the category field's schema is an unconstrained anyOf string with no enum, and the description supplies the authoritative list of seven beats. It does not explain the limit parameter's interaction with categories, keeping it from a 5.

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 ('Today's top SkimNews stories'), plus scope ('today') and the optional beat narrowing. An agent can distinguish it from get_story_detail (single story) and search_stories (query-driven) 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?

Explicitly maps the tool to user intents: "what's happening today" / "today's news" / "latest in <beat>". That is clear when-to-use guidance, but it never names an alternative (search_stories) or a when-not condition, so it stops short of full routing guidance.

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