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

Annotations already declare readOnlyHint=true, openWorldHint=true and destructiveHint=false, so the safety profile is covered. The description adds genuine non-obvious context: the forecast horizon is capped at 16 days, climate values are 5-year averages, sea temperature is included, and the FX rate is the Central Bank rate — real behavioral limits the annotations do not express.

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 front-loaded sentence that opens with the subject (destination reference for a Russian tourist) then lists the payload items. Dense but with no filler; a short second sentence about limits or output shape would have helped, but nothing here is wasted.

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 no output schema, the description carries the burden of describing returns, and it does so item-by-item (visa, weather, time zone, currency/FX). It stops short of stating the response structure or behavior for unknown destinations, but an agent has enough to call it correctly.

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 the baseline is 3. The description goes further by explaining the semantics behind the parameter choice: date_from/date_to yield a forecast (limited to 16 days) while month yields 5-year climate averages, which tells the agent why the month fallback exists and when each 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 a specific resource (destination reference data) and enumerates the exact payload: visa requirements for RF citizens, weather forecast or monthly climate, time difference with Moscow, local currency and CB exchange rate. This is clearly distinguishable from siblings like search_flights, cheapest_prices and find_city, which are transactional rather than informational.

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?

Usage is only implied: the forecast-vs-climate wording hints that exact dates select a forecast and a bare month selects averages, but there is no explicit when-to-use statement or named alternative. Siblings are adjacent (city lookup, pricing) yet no routing guidance is offered.

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