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

With no annotations, the description fully explains the unusual payment process (first call without payment_signature returns requirements). It also mentions the paid model. However, it does not state that the tool is read-only or describe any side effects.

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: the first states the tool's core function, the second covers payment details. It is front-loaded and concise, though the payment flow could be formatted more explicitly.

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 simple forecast tool with 3 parameters, the description covers location, days, and the payment process adequately. No output schema exists, but the description hints at return fields (temperature, precipitation, etc.). It could mention pagination or response format.

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 coverage is 100%, so baseline is 3. The description adds value by clarifying the default days (7), maximum (16), and the detailed payment flow for the payment_signature parameter, which is more context than the schema alone.

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 states it provides a 16-day weather forecast for any location, listing specific data points (temperature, precipitation, wind, UV index). It distinguishes from the sibling tool 'get_weather_history' by focusing on future forecasts.

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 mentions the paid nature and payment flow but does not explicitly contrast with sibling weather tools like 'get_weather_history' or provide when-to-use/not-use guidance. Usage context is implied but not explicit.

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