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

Annotations already declare readOnly, idempotent and closed-world, so the description only needs to add context. It does: it discloses what is returned (edition, change notices of amending decrees, sub-article titles, PlanElec link) and the non-obvious language fallback where English resolves to the German text. It says nothing about behavior for a missing or invalid article number, which keeps it from 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?

Front-loaded with the core action, then two short follow-up sentences on citation and sibling routing. The opening sentence is dense but each clause (scope, formats, language, returned fields) carries information an agent would otherwise have to guess; no filler.

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 an output schema, full annotation coverage and 100% schema description coverage, the description supplies everything else an agent needs: scope limitation to Book 1, supported languages and fallback, edition behavior, and the discovery path via search_regelwerk.

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%, so the schema carries the baseline. The description still adds meaning beyond it: accepted article-number shapes including a prefixed form like "AREI 7.1.4.3", and the language-resolution rule that English falls back to German text, which the locale enum alone does not convey.

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: returns the text of one article of Book 1 of the Belgian AREI/RGIE, identified by its number. It gives concrete number formats and names the sibling search tool, so an agent can distinguish it from search_regelwerk immediately.

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?

Explicitly routes discovery to the alternative: "Use search_regelwerk to find the number." It also gives a downstream usage rule — cite the article number and edition when passing content on — which is exactly the when/how guidance an agent needs.

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