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

Annotations already indicate readOnlyHint=true, idempotentHint=true, and destructiveHint=false, so the safety profile is clear. The description adds meaningful behavior context beyond annotations: the data source (Meteostat), licensing (CC BY 4.0), the fact that no authentication is required, and that the history can span many decades. This tells the agent what to expect in terms of data provenance and request setup.

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 sentences with no filler. The main action and result are front-loaded, followed by the parameter source and then data provenance/licensing. Every sentence earns its place and the structure is easy to scan.

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 single-parameter read-only tool with a rich output schema and full annotations, the description covers everything needed: what data is returned, where the station ID comes from, licensing, and auth requirements. Nothing an agent needs to correctly invoke this tool is missing.

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% — the station_id parameter description already states it comes from meteostat.stations_nearby and returns the full monthly history. The tool description repeats this info rather than adding new parameter-specific semantics. With the schema covering the parameter fully, the baseline of 3 is appropriate.

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 uses a specific verb and resource: 'Get the full monthly weather history' and lists the exact variables returned (mean/min/max temperature, precipitation, pressure, sunshine). It clearly distinguishes from sibling tools like meteostat.observations.daily and hourly by specifying 'monthly'. The scope is explicit — a single weather station, potentially spanning decades.

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 clearly provides the prerequisite for using the tool: 'Station ID comes from meteostat.stations_nearby.' This tells the agent how to obtain the required parameter and implies the intended workflow. However, it does not explicitly mention when not to use this tool or name alternatives like daily/hourly observations for finer granularity, so it falls just short of a 5.

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