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

The readOnlyHint annotation already establishes this as a safe read operation. The description adds value by enumerating the return contents (title, body, author, clinical reviewer, citations, metadata), informing the agent what to expect. It does not mention error cases or rate limits, but for a simple fetch tool this is acceptable.

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?

The description is a single, front-loaded sentence that communicates the core function and return fields with no filler. Every piece of information is necessary and directly 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?

Given the simplicity (one parameter, no output schema) and the presence of a readOnlyHint, the description fully covers what the tool does and what it returns. An agent has sufficient information to select and invoke this tool without additional documentation.

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 schema covers the single parameter 'slug' with a brief description. The tool description reinforces that the slug identifies an article but adds no additional semantic detail such as format, length, or source. Since schema coverage is 100%, the baseline of 3 applies.

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?

The description clearly states the action ('Fetch'), the resource ('a single article'), and the identifier ('by slug'). This distinguishes it from sibling tools like list_articles and search_articles, which retrieve multiple articles, and cite_article, which focuses on citations.

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 description implies when to use this tool (when you have a specific slug and want one article) but does not explicitly contrast it with alternatives such as list_articles or search_articles. No 'when not to use' guidance is provided, but the 'single... by slug' phrasing provides a clear enough context.

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