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

Annotations already declare readOnlyHint=true and openWorldHint=true, so the description does not need to re-state read-only behavior. It adds valuable context about the external dependency (Open-Meteo) and the lack of authentication, which goes beyond the annotations and helps the agent set expectations about network access and reliability.

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 two sentences, with the primary purpose front-loaded and the essential usage constraints stated compactly. No filler or redundancy; every sentence adds necessary information.

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 details are not needed. The description covers purpose, input formats, external service, auth requirements, and a critical limitation. It could mention units (Celsius/Fahrenheit) or timezone handling, but these are minor and not essential for correct invocation. Overall, it is complete for a simple read-only tool.

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 already describes both parameters thoroughly (location with examples, days with range and default). The description repeats the location format and adds the 'no device-location access' caveat, but that is more behavioral context than parameter semantics. Since schema coverage is 100%, a baseline of 3 is appropriate; the description does not meaningfully enhance parameter understanding.

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 ('Gets') and resource ('current weather and a short daily forecast for a location'), which is clear and unambiguous. It also includes concrete input formats (city name or coordinates) and names the external service (Open-Meteo), making the tool's function immediately evident even among a large sibling set.

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 explicitly tells the agent how to provide the location (city name or lat,lon), states that no API key is required, and highlights that a location must be provided because there is no device-location access. This gives clear, actionable guidance with no ambiguity.

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