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

Annotations already declare readOnlyHint, idempotentHint, destructiveHint=false, and openWorldHint=false, so the safety profile is covered. The description adds value beyond that by stating determinism and concrete operational limits (64 KB input, 1 s per call, 1 MB result), which annotations cannot express. Minor overlap on 'no state saved' with the read-only hints keeps it from a 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?

Labeled segments (Cuándo / No para / Efectos / Determinista / Límites) make it scannable and the purpose is front-loaded. The full bilingual duplication roughly doubles the length, which costs a point but is a deliberate, consistently structured pattern.

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?

With an output schema present, return values need not be explained, and the description covers side effects, determinism, and resource limits. Nothing essential for correct invocation is missing, though edge behaviors (e.g., out-of-zone easting validation errors) are left entirely to the schema bounds.

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 zone, easting, northing, and hemisphere including the band-letter pattern. The description's mention of 'hemisferio o banda' restates what the schema's pattern encodes, adding no new format or interpretation guidance. 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 and resource pair: convert UTM (zone, hemisphere or band, easting, northing) to WGS84 lat/lon. It also names the inverse sibling utm-from-latlon, so an agent can distinguish the two without opening either 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?

The 'Cuándo' line gives the triggering context (computing coordinates, distances, bearings, areas from given points) and 'No para' explicitly routes to utm-from-latlon for the opposite direction. When-to-use, when-not, and the alternative are all named.

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