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

No annotations are provided, so the description carries full responsibility. It discloses that no API key is needed, that data is real-time and always up-to-date, and lists returned fields. However, it does not mention potential error behaviors, rate limits, or latency, leaving some 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 description is brief at three sentences, front-loads the primary action, and contains no redundant phrases. Every sentence earns its place by describing purpose, bridging Claude's limitation, and listing outputs.

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?

Though no output schema exists, the description compensates by listing the key return fields (current conditions, temperature, etc.) and stating the tool's reliability. For a simple weather tool, the context is adequate, though it could mention possible errors or formatting.

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 schema already documents both parameters thoroughly. The description reiterates the parameter meanings (e.g., 'unlimited, always up-to-date') but does not add new semantic value beyond the schema.

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 'Get real-time weather for any city, anywhere in the world' with a specific verb and resource. It lists the outputs (current conditions, temperature, humidity, etc.) and there are no sibling weather tools, so differentiation is not needed.

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 explains that Claude lacks live data access and this tool fills that gap, making the use case clear. It promotes free and unlimited usage but does not explicitly provide alternatives or exclusion criteria, though none are necessary given the sibling context.

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