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

Annotations already declare readOnlyHint=true, idempotentHint=true, and destructiveHint=false. The description adds meaningful behavioral context beyond annotations: 'no auth required', the CC BY 4.0 data license, and the 7-day/single-year constraint. It does not contradict the annotations and provides useful operational details.

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 three sentences, each contributing substantive information: what the tool returns, the scope/prerequisite, and the alternative + licensing/auth note. It is front-loaded with the primary action and only includes necessary details, though slightly more verbose than the two-sentence gold standard.

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 3-parameter tool with an output schema, the description adequately covers scope constraints, prerequisite station ID source, alternative for longer spans, and data licensing/auth. It does not need to describe return values due to the output schema. Minor omissions like units/timezone are not described, but likely covered elsewhere.

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%, with each parameter already documented (station_id source, start/end format and constraints). The description repeats these constraints (e.g., 'up to 7 days') but adds no significant parameter-level information beyond the schema. Baseline 3 is appropriate because the schema carries the load.

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 states a specific verb+resource ('Get hourly weather observations') and enumerates the meteorological variables included (temperature, humidity, precipitation, wind, pressure, cloud cover, weather condition code). It clearly distinguishes from sibling tools by noting the 7-day/single-calendar-year scope and explicitly referencing meteostat.daily_data as the alternative for longer spans.

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?

It provides explicit guidance on when to use this tool vs alternatives: 'Use meteostat.daily_data for longer time spans' and 'Station ID comes from meteostat.stations_nearby' (a prerequisite). It also mentions data attribution and auth requirements, leaving little ambiguity about when to invoke this tool.

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