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

With no annotations provided, the description carries the full burden. It successfully discloses geographic constraints (US only) and temporal limits (up to 7 days), but omits mutation safety (implied by 'Get'), rate limits, or error behavior for out-of-bounds coordinates.

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?

Three sentences with zero waste: sentence 1 establishes purpose and scope, sentence 2 provides usage context, and sentence 3 clarifies output granularity. Information is front-loaded with the action verb.

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 2-parameter tool with 100% schema coverage and simple types, the description is sufficiently complete. It partially compensates for the missing output schema by mentioning 'detailed day/night forecasts,' though it could specify the return structure (e.g., JSON with temperature/precipitation fields).

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 reinforces the 'days' parameter ('up to 7 days') and 'location' parameter ('US location') but does not add syntax details, validation rules, or examples beyond what the schema already provides.

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 opens with a specific verb ('Get') and resource ('multi-day weather forecast'), explicitly scopes the tool to US locations, and distinguishes it from siblings like get_current_weather and get_hourly_forecast by emphasizing 'day/night' forecasts 'up to 7 days'.

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 phrase 'Perfect for "What's the forecast for [US location]?" questions' provides a clear query pattern for selection. While it does not explicitly name sibling alternatives, the 'multi-day' and 'day/night' phrasing implicitly signals when to use this over hourly or current weather tools.

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