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

The description goes beyond the annotations by disclosing that it is read-only, that purchases via the linked merchant are affiliate-based with unchanged prices, that it searches the full catalog (several hundred products), and that it returns facets for refining filters. It also mentions the 30-day price trend and the direct purchase link, all of which are behavioral traits not covered by annotations. No contradiction exists.

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 informative but redundant because it repeats the same content in German and English. While the structure is front-loaded with the main purpose and the English summary provides a quick overview, the duplication inflates the length. It could be more concise by keeping only one language or a shorter summary.

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?

The description covers usage conditions, output fields (title, best price, brand, image, 30-day trend, attributes, url, detailUrl, facets), and behavioral notes (read-only, affiliate, full catalog). The output schema also exists, so return values are well documented. For a search tool with optional parameters, this is complete.

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 description coverage is 100%, so the schema already documents each parameter (brand, limit, query, minPrice, maxPrice) with descriptions. The description mentions that filtering is possible by search term, brand, and price range, and that brand values come from facets.marke, but this is already in the schema. The description adds no significant parameter-level detail beyond what the schema provides, 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 clearly states a specific verb and resource: it searches for solar systems (Solaranlagen) and finds the cheapest current price across Amazon, eBay, and AliExpress in Germany. The scope, marketplaces, and purpose are explicit. It is easily distinguished from the sibling lookup_product, which implies a single-product lookup, while this is a multi-product search tool.

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 explicitly states when to use this tool: 'Nutze dieses Tool, wenn ein Nutzer nach Preis, Angebot, "guenstig", "wo kaufen" oder einem konkreten Solaranlage fragt.' This is a clear trigger condition. It does not explicitly mention when not to use it or name alternatives, but the condition is specific enough to guide an agent.

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