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

Annotations already declare readOnlyHint, idempotentHint, openWorldHint and destructiveHint=false, so the description correctly does not restate safety. It adds real context beyond them: the data source (ЕГРЮЛ/ЕГРЮП registries) and the concrete set of returned attributes, which matters because no output schema exists. It omits not-found/error behavior, 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?

A single compact sentence front-loads the returned fields, then the lookup key, then the use case. No filler, no repetition of the title or of annotation data.

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 one-parameter, read-only lookup with full annotation coverage, the definition supplies what an agent needs: what comes back and what the key means. The absence of an output schema is partly offset by the enumerated return fields. Only edge-case behavior (invalid or unregistered INN, partial data) is unaddressed.

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% and the schema itself explains the 10-digit organization vs 12-digit individual-entrepreneur distinction. The description reinforces this with 'организации или ИП', but adds no format, validation, or failure-mode detail beyond the schema. 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?

The description names the exact resource (organization or individual entrepreneur record) and the lookup key (INN), and enumerates the fields returned: name, KPP, OGRN, address, status. The action verb is only implicit (a list of outputs plus 'по ИНН'), and no sibling tool is named, but none of the listed siblings performs registry lookup, so confusion risk is low.

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?

'— для счёта' hints at the billing/invoice context in which this lookup is appropriate, which is genuine when-to-use signal. However, there are no exclusions, no stated prerequisites (e.g. what to do if the INN is unknown), and no comparison to alternatives such as store_info.

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