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

Annotations already cover the safety profile (readOnly, idempotent, non-destructive, closed-world), so the bar is lower. The description goes beyond them by disclosing what the payload contains for each id type — summary, context, cross-portal duplicates, location, or full story timeline. It does not mention rate limits or auth requirements, but that is minor for a read tool.

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 sentence that front-loads the core action and then lists return contents economically. The parenthetical prefix forms and the colon-list are dense but readable; nothing is wasted.

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 is not obligated to explain return values yet it still characterizes them usefully. Combined with annotation and schema coverage, an agent has enough to invoke this correctly; the only gap is the missing routing rule versus get_article and get_story_timeline.

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 already 100% with a single documented 'id' param, so baseline is 3. The description adds real value beyond 'An id from search' by specifying the required 'article:…' or 'story:…' prefix formats, which is information the schema does not carry.

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 one result of search by its id') and enumerates what the prefixes return (article summary/context/other portals/location, or a story timeline). This clearly separates an article-prefixed id from a story-prefixed id. It stops short of naming the closely related siblings get_article and get_story_timeline, so an agent still has to infer which one to prefer.

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 phrase 'one result of search by its id' implies the tool is used downstream of search, which is the key context. However, there is no explicit when/when-not and no routing guidance against get_article or get_story_timeline, which appear to cover overlapping ground.

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