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

Goes well past the readOnly/idempotent/openWorld annotations: discloses the NOAA source, up-to-5-minute caching, found:false for stations with no report, the 422 invalid_station and 503 upstream_unavailable error semantics with 'not charged' billing behavior, latency expectations, and a prompt-injection advisory to treat report text as data. This is unusually complete behavioral disclosure.

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?

Purpose is front-loaded and virtually every clause carries operational value (pricing, errors, caching, safety). The cost is a single dense semicolon-chained block with no paragraphing, which is heavier to parse than it needs to be for the amount of distinct information.

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?

There is no output schema, so the description carries the return-value burden and does so fully — raw plus decoded fields, per-station found flag, station metadata. Combined with documented error codes and latency, an agent has everything needed to call and interpret this tool.

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 already 100%, so the baseline is 3, but the description adds real meaning: one price covers 1-20 stations, ICAO ids must be 4 characters, and a malformed id yields 422 invalid_station rather than a partial result. The decode default of true is restated rather than extended, keeping it short of a 5.

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 and resource — 'the latest METAR observation for 1-20 ICAO stations' — and enumerates exactly what comes back (wind, visibility, weather, clouds, temperature/dew point, altimeter, flight category, station name/position/time). The 'latest observation' scope inherently separates it from forecast-oriented siblings like get_taf.

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?

Gives clear context for use (current station weather) plus an explicit exclusion: 'Informational only: not for flight planning or navigation.' However, it never names an alternative such as get_taf for forecasts or decode_metar_taf for decoding a raw METAR string the caller already has, so routing between near-siblings is left to inference.

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