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

Since no annotations are provided, the description must carry the behavioral burden. It does reveal the output unit (days) and a flat cost ($0.01 USDC), but it does not mention any side effects, required permissions, behavior on invalid or nonexistent indices, rate limits, or whether the operation is read-only. The cost disclosure is helpful but leaves major gaps.

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 full content is a single line with no filler: the core function, the output unit, and the cost. It is succinct and front-loaded, maximizing clarity per word.

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 tool with generic input schema, no output schema, and no parameter documentation, the description omits critical context: the exact structure and types of the postal indices, the response format beyond a count in days, and behavior for invalid inputs. An agent cannot confidently determine the correct call or interpret the result.

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?

The input schema offers only generic 'args' and 'extra' objects with no property descriptions (0% coverage). The description hints that the tool needs two postal indices, but it does not explain how those indices should be structured within 'args' or whether 'extra' is required. The agent cannot reliably know how to construct the request.

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 clearly identifies the function: delivery times between postal indices in days, and scopes it to Russian Post (Почта России). This distinguishes it from sibling tools like pochta_tariff (pricing) and pochta_track (tracking), though it lacks an explicit verb like 'calculates' or 'estimates'.

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 about when to choose this tool over alternatives such as pochta_tariff or pochta_offices. The description states only what the tool returns, not in which scenario a caller should invoke it, nor any conditions or prerequisites like requiring two indexes.

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