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

Annotations already declare readOnly/idempotent/non-destructive/closed-world, so the safety profile is covered. The description adds genuine value beyond them by enumerating the response contents (summary, headings, excerpt, legal references, PL/EN/DE versions), which tells the agent what it will get back — the main behavioral unknown 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?

Two sentences, zero filler, with the core operation front-loaded and the language-version note trailing as a secondary hint.

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?

There is no output schema, so the description must characterize the return value — and it does so concretely with the list of article parts plus the available language versions. Missing only edge behavior (what happens on unknown slug, whether lang falls back) for a full 5.

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%, including descriptions for both url ('URL on supplemental.pl or its slug') and lang ('Response language. Default: en.'), so the schema carries the load. The description only restates these ('by URL or slug', 'Pass lang to get another language version') without adding format detail, 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: 'Return one supplemental.pl knowledge article by URL or slug.' The word 'one' plus the enumerated return contents distinguishes it from the sibling search_articles without needing to name it.

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 only usage guidance is the conditional 'Pass lang to get another language version', which is helpful but parameter-level. Nothing states when to use this versus search_articles (e.g. 'use when you already have a URL/slug').

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