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

Annotations already declare readOnly, idempotent, openWorld and non-destructive, so the safety profile is covered. The description adds genuinely new behavioral context that structured fields do not: the cost model ('free within the daily allowance, then $0.003 USDC per call via x402'), which tells the agent about rate limits and paid overflow. It doesn't, however, describe response granularity or time-horizon behavior.

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 tightly packed sentences with no waste: content scope first, commercial constraint second. Every clause earns its place and the most decision-relevant information is front-loaded.

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?

With an output schema present, return values need no explanation, and annotations cover the safety profile; the description supplies the missing pieces (forecast fields, pricing/allowance). The remaining gap is the absence of explicit differentiation from global-weather__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% (both lat/lon documented), so the schema already carries parameter meaning and baseline is 3. The description adds nothing about coordinate format, units, or expected ranges, so it neither helps nor hurts.

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 ('Full forecast') and enumerates the fields it adds (humidity, pressure, fog, UV, precipitation ranges), so the agent knows this is the detailed variant. However, it never names the sibling global-weather__forecast or explicitly contrasts itself with it, so differentiation must be inferred from 'Full'.

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 word 'Full' implies this is the richer option versus global-weather__forecast, but there is no explicit when-to-use/when-not guidance, no statement of prerequisites (beyond the cost note), and no named alternative. Usage is only implied.

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