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

Annotations already declare readOnly, idempotent, openWorld, non-destructive, so the safety profile is covered. The description adds genuine behavioral context beyond that: data sources (MET Norway worldwide, NWS for U.S.), the extra narrative forecast and active alerts for U.S. locations, and the unit conventions. It does not discuss rate limits or failure modes, but the added sourcing detail is substantive.

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?

Two dense sentences, front-loaded with the capability and then the source/regional caveats; little waste. The parenthetical field list is compact rather than padding, though the single long second sentence is somewhat overloaded.

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?

An output schema exists, so return-value documentation is unnecessary. For a zero-required-parameter, read-only lookup the description covers output scope, units, sources, and regional behavior well. The main gap is routing versus overlapping siblings like get_airport_forecast.

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 adds only marginal semantic value — it clarifies that coordinates or an airport code are the locators and that output is in °C and °F — but says nothing about the roles of tz, name, or precedence between airport and lat/lon.

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?

States a specific verb+resource with rich scope: current conditions, 12-hour and up-to-9-day forecast, coordinates or airport, °C and °F, with named data sources. An agent immediately knows what it returns. However, it never distinguishes itself from the sibling get_airport_forecast despite accepting an 'airport' parameter, leaving overlap unresolved.

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 — 'weather anywhere' suggests it is the general-purpose weather tool, but there is no explicit when-to-use guidance and no mention of when to prefer get_airport_forecast, get_airport_status, or check_trip_delay_risk. Alternatives in the sibling list go unaddressed.

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