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

Annotations already cover read-only/idempotent/open-world safety, and the description adds information the annotations cannot: cost (0.003 USDC per call), p95 latency (1500 ms), source attribution and the coordinate input requirement. It does not describe forecast granularity or max horizon, though the schema parameter does.

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?

Front-loads the return payload, then use/do-not-use, then cost and latency – a sensible order. Slightly dense with the field enumeration, but every clause carries operational value.

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 agent has everything needed: what it returns, coordinate constraints, when to pick an alternative, the geocode prerequisite, cost, latency and a full output schema. No material gap.

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 the baseline is 3; the description still adds the coordinate framing and notes place names must be geocoded first, which clarifies that no name parameter exists anywhere.

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 (returns) and resource (hourly weather forecast), enumerates the returned fields, names the data source (MET Norway), and distinguishes its scope from siblings by ruling out historical weather and alerts.

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?

Explicitly says when to use ('weather forecast, temperature or precipitation for the next hours or days at a place given by coordinates') and when not to use (historical weather, severe alerts, place names), plus the remediation: geocode the name first.

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