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

Annotations already establish read-only and idempotent behavior, lowering the bar. The description adds meaningful behavioral context beyond annotations: it enumerates that primary, star, additional, and second-primary key numbers are all considered, and explains that the result is every string in the alphabetical index referencing the code. It does not cover edge cases like missing codes, but the output schema handles return structure.

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 reasonably compact: a German sentence stating the core behavior, a second sentence adding key-type coverage, and an English summary that repeats the main idea for bilingual accessibility. Every part carries substantive information; the bilingual duplication is a minor inefficiency rather than fluff.

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 simple read-only reverse lookup with two parameters, full schema coverage, and an output schema present, the description is nearly complete. It explains what the tool returns, which key types are included, and the practical use case. It doesn't mention invalid-code behavior or year availability, but these are minor gaps given the annotations and schema already cover safety and parameter constraints.

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?

Input schema description coverage is 100%, and both parameters ('code' and 'year') are already explained in the schema with examples and defaults. The tool description adds no further parameter-level semantics, so 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 uses a specific verb ('Liefert') and resource ('Einträge des Alphabetischen Verzeichnisses') tied to a clear lookup criterion (a given ICD-10-GM code). It precisely distinguishes this reverse-lookup tool from forward lookups or text searches by stating it returns every wording that points to the code, covering primary, star, additional, and second-primary keys.

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 clearly frames the intended use: given an ICD-10-GM code, discover all index wordings that lead to it, especially useful for seeing covered clinical and everyday terms. It implies the alternative is a text-based search over the alphabetical index (e.g., icd10alpha_search) without naming it explicitly, and it does not state when-not-to-use exclusions, so it stops short of a 5.

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