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

No annotations are provided, so the description carries full responsibility. It discloses the cost ($0.01 USDC), which is useful, but does not state that it is a read-only operation, what happens with invalid indexes, whether authentication is needed, or any rate limitations. The safety profile is largely undisclosed.

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 a single short sentence that leads with the purpose and includes the cost. It is efficient and free of fluff. However, it under-specifies important details, so while concise, it is not backed by supporting structure like parameter notes.

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?

Given a 4-parameter tool with 0% schema coverage, no output schema, and no annotations, the description is severely insufficient. It omits parameter semantics, expected output, error handling, and any usage conditions. An agent would struggle to call this tool correctly without external knowledge.

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% and the description mentions none of the four parameters (from_index, to_index, mail_type, mail_category). It does not explain what these values represent or how to format them. The description fails to compensate for the missing schema documentation.

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 a specific verb ('delivery times') and resource ('between indexes'), and mentions the unit ('in days'). It conveys the core function clearly and is distinct from siblings like pochta_tariff (tariffs) and pochta_track (tracking). However, it doesn't explicitly name alternatives or differentiate itself, so it falls short of a 5.

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?

No guidance is given on when to use this tool compared to siblings like pochta_tariff or pochta_delivery. There are no exclusions, prerequisites, or suggested contexts. The description merely states what it does without any usage direction.

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