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

Annotations already declare readOnly, idempotent, non-destructive and closed-world, so the safety profile is covered. The description adds genuinely non-obvious behavior: content is in Russian, an English query does not imply an English-language tour, and there is no live availability — all of which change how an agent interprets results. It stops short of describing result shape or result-count behavior, keeping it below 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?

Three sentences, front-loaded with the resource enumeration and closing with the constraints that most affect interpretation (Russian language, no booking). The opening service list is long but functional for semantic matching; nothing reads as filler, though the density is close to the limit.

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?

With no output schema, the description does some work on return content by mentioning author descriptions, Felix's guide profile and qualified terms, and it flags the important language caveat. For a three-parameter read-only catalog tool this covers what an agent needs, with the only soft spot being how large the catalog results are.

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 67% and the query parameter has no schema description at all, so the description carries real weight here. It explains that query and city are optional filters, that service_id must come from a catalog, and that omitting all arguments falls back to the general catalog — meaning that is not derivable from the bare schema.

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?

"Find a professional guide, an individual city tour, an evening tour, a beer tasting or a transfer in Belgium" gives a concrete verb and enumerates the resource types, so an agent knows exactly what this returns. It also implicitly separates itself from the prepare_* siblings by stating there is no booking or payment, though it never names those siblings directly.

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?

"Use optional query/city filters or a service_id from catalog for the complete program; no arguments preserve the general tour/transfer catalog" tells the agent both the filtered and the no-argument modes, which is actionable when-call guidance. What is missing is an explicit pointer to the alternatives (get_answer, search_knowledge, prepare_tour_request) for the cases this tool does not cover, even though the "no booking/payment" clause hints at the split.

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