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

With no annotations, the description carries the full burden and does so well: it discloses that callers need their own MapMap key, that the MapMap gateway is required, that values are quantised/regridded, that the `status` field signals run freshness, and that `attribution` must be displayed. That is meaningful behavioral context beyond the schema. It stops short of failure modes, caching, or rate limits, keeping it at a strong 4 rather than 5.

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?

Effectively one dense paragraph that front-loads what the tool returns before the licensing/attribution caveats. Most sentences earn their place (field list, decoding hint, key requirement), though the legal caution ('never describe it as original NOAA data...') is asserted twice and adds bulk.

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?

Given an output schema exists, return values need not be explained here, and the description still supplies the operational essentials: auth key, gateway dependency, encoding/decoding, and attribution. It is close to complete for a data-fetch tool, with only edge-case behavior (invalid run, empty fields) left unaddressed.

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 the schema already documents `run` (YYYYMMDDHH, default newest) and `fields` (default all). The description restates the format and defaults but adds no syntax or constraint detail beyond what the schema provides, so the baseline 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 opens with a precise verb+resource framing: the NOAA GFS forecast frames MapMap publishes, and enumerates exactly what is returned (17 frames, 0–48h at 3h steps, PNG fields, wind JSON ranges, XYZ tile templates). An agent can immediately distinguish this bulk frame/URL product from point-based siblings like weather_along_route or space_weather_now.

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 disambiguates the data type ('A FORECAST, not an observation') and notes the optional `run`/`fields` defaults, which implies the intended use (fetching map-drawable forecast frames). However, it never names an alternative sibling or states when NOT to use this tool versus weather_along_route, leaving selection largely to inference.

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