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

Annotations already declare readOnlyHint=true, so the safety profile is covered structurally. The description adds real value beyond that by disclosing the underlying endpoint and the response envelope shape ({ valid, data:{...} }), which matters because no output schema exists. It does not cover failure modes for an unknown id, keeping it below a 5.

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 short sentences with the purpose front-loaded and nothing padded. The endpoint sentence is marginal but provides traceability to the upstream API; the whole definition can be read in a couple of seconds.

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 one-parameter read tool this covers the essentials: what it fetches, the key, and the return envelope despite there being no output schema. Missing only failure behavior (e.g., response when the id does not resolve), which keeps it from top marks.

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 single 'id' parameter is already documented as a Mongo-style hex string in the schema. The description only restates 'by id' and adds no format, constraint, or example beyond that, so baseline 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?

States a specific verb and resource ('Fetch a single article by id'), and the word 'single' implicitly separates it from the list_articles siblings. It stops short of naming an alternative explicitly, so the sibling differentiation is inferred rather than stated.

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?

Usage is only implied: an agent can reason that this is the by-id lookup rather than a listing call. There is no explicit when-to-use / when-not-to-use guidance, no mention of error behavior for a missing id, and no pointer to list_articles or list_article_revisions as alternatives.

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