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

There are no annotations, so the description carries the behavioral disclosure burden. It usefully discloses that the lookup costs $0.01 USDC and that it returns both office address and locality. It does not mention failure behavior, required authorization, or whether the tool performs an external API call, but the core read-only nature is implicitly clear.

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 one concise sentence plus a cost note. It front-loads the core purpose and adds only the relevant pricing detail, with no filler or redundancy.

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 single-parameter lookup with no output schema and no annotations, the description is minimal but broadly sufficient: it states what the tool does and its cost. It lacks explicit notes on return format, invalid postal codes, or whether the output is structured, which an agent might need for robust handling.

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 0%, so the description must compensate. It adds that postal_code is an 'индекс' (Russian postal index) and ties it to the returned address/locality. However, it does not specify the expected format (e.g., 6 digits), validation rules, or any normalization behavior.

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 states the resource (address of a Russian Post office and the locality) and the query criterion (по индексу / by postal code), so an agent can understand what the tool returns. It does not explicitly distinguish itself from sibling tools like pochta_address or pochta_offices, but the 'по индексу' scope is reasonably specific.

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 implies the tool should be used when an agent has a Russian postal code and needs the associated post office address and locality. However, it provides no explicit guidance about when to prefer this over siblings such as pochta_address or pochta_offices, nor any exclusions.

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