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

Annotations already declare readOnlyHint, idempotentHint, destructiveHint=false and openWorldHint=false, so the safety profile is fully covered by structured data. The description adds nothing behavioral beyond that – no not-found behavior, no auth/permission requirements, no rate-limit or payload context.

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?

Two short sentences with the purpose front-loaded and no filler. The API doc URL is arguably of limited value to an agent, but it costs little and adds traceability.

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 with a full output schema and rich annotations, the description supplies what is needed to invoke it correctly. Missing only edge-case behavior (unknown ArticleNumber) which is not covered anywhere else.

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 parameter is documented as 'identifies the article'. The description's {ArticleNumber} path reference adds mild confirmation that the value is the Fortnox article number used in the URL, but nothing about format or validation. Baseline 3 applies since the schema does the work.

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?

Specific verb+resource ('Retrieve an article') plus the exact upstream endpoint GET /3/articles/{ArticleNumber}, so an agent knows it is a single-record fetch. It does not explicitly distinguish itself from the sibling list_articles, leaving the singular-vs-list split to inference.

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: the required ArticleNumber and the {ArticleNumber} path segment signal 'use this when you already have an identifier, otherwise use list_articles'. There is no explicit when-to-use/when-not statement or named alternative.

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