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

Goes well beyond the readOnly/idempotent/openWorld annotations: discloses 5-minute cache TTL, latency (~2 s, <0.1 s cached), pricing (USD 0.001, free 5 calls/IP/UTC day shared pool), error semantics (422 invalid_station and 503 upstream_unavailable, both uncharged), and a prompt-injection warning that quoted report/alert text must be treated as data. This is rich behavioral context an agent needs to call and interpret the tool safely.

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 and inputs are front-loaded in the first sentences, and most sentences earn their place (errors, pricing, latency, safety). There is mild redundancy, e.g. pricing is stated twice ('One price for 1-20 stations' and 'Price: USD 0.001'), which keeps it from a 5.

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?

No output schema exists, but the description fully enumerates the returned content (raw + decoded per period, wind, visibility, weather, clouds, flight category, issue/validity times, temperature extremes), plus cost, latency, and failure modes. Nothing an agent needs in order to invoke and interpret it 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%, so both parameters (stations, decode) are already documented in the schema, including the decode default and the array bounds. The description restates the ranged station input and one-price-per-call semantics but adds no format or syntax detail beyond the schema, so the baseline 3 applies.

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 (current TAF forecasts for 1-20 ICAO stations) with the decoding granularity (BASE, FM, TEMPO, BECMG, PROB) and the returned fields, so it is clearly distinguishable from siblings like get_metar and decode_metar_taf. An agent knows exactly what it fetches without opening the schema.

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?

Provides a clear when-not ('Informational only: not for flight planning or navigation') and states the 1-20 station batching use case plus the free-tier/informational context. It stops short of explicitly routing to the closest alternatives (get_metar for METAR, decode_metar_taf for decoding), so it falls 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.