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

Annotations already declare readOnly, idempotent, non-destructive, closed-world behavior, so safety is covered. The description adds genuinely non-structured context: the corpus is 'collected' (a subset, not the registry) and negative results are not authoritative — important framing for how much to trust an empty response. Return format and pagination are left to the output schema.

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 and only three short sentences, each carrying information (scope, exclusion, negative-result caveat). The trailing Russian sentence duplicates the opening English sentence rather than adding new content, which is mild redundancy for an agent parsing the description.

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 annotations covering the safety profile and an output schema covering return values, the description fills the remaining gaps an agent needs: what the corpus is, what can be found by name, and how to interpret a negative result. Explicit guidance on the lookup_company/check_counterparty fallback for sole proprietors would make it fully self-contained.

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 both parameters (query, limit) are already documented in Russian with format hints, defaults, and the 1–25 range. The description restates that query accepts a name fragment or UNP and adds no syntax or matching rules (e.g., case sensitivity, prefix vs substring) beyond what the schema provides. 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 concrete verb (search) plus the resource (collected Belarusian legal entities), and names both lookup keys: name fragment or UNP. The sentence 'Only legal entities are found by name (sole proprietors never are)' scopes the tool against the sole-proprietor path handled by siblings like lookup_company, so an agent can distinguish it without opening the schema.

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?

Gives clear context for when the tool applies (name-fragment or UNP lookups over the collected corpus) and the crucial caveat that a miss here does not mean the entity is absent from the state registry — 'Absence here is not absence in the state registry.' It stops short of explicitly routing sole-proprietor-by-name cases to an alternative tool in the description body; that routing only appears in the schema's query description.

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