Itu Zones Lookup

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

Annotations already declare the safe read-only, idempotent, closed-world profile, so the description is free to add real substance: it discloses that zones 76-77 and 79-89 have no entry in this edition, which prevents a false negative from being read as a bug. It still doesn't say whether a missing zone raises an error or returns empty.

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, no filler, payload front-loaded (what one record contains) followed immediately by the caveat. Both sentences earn their place.

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 a single param, full annotations and an output schema, the description carries enough: content of the record plus the coverage gap. The one unresolved point is the failure mode for the excluded zones, which an agent must guess.

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 100% and the code param is documented as 1-90, so the baseline is 3. The description earns above that by naming the specific codes in that range which yield no entry, giving the agent information the schema does not carry.

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 resource and scope: a single ITU zone with every prefix, subdivision, boundary, ADIF code and citation the IARU lists. That reads clearly against the plural/search siblings (itu_zones_search, itu_zones_codes_for). No verb is used ("One ITU zone: ..."), and it never explicitly names which sibling to use instead, so it stops short of a 5.

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?

Usage is only implied by the singular framing ("One ITU zone") contrasted with the search/codes_for siblings; it never says when to prefer this over itu_zones_search or itu_zones_valid_on. No prerequisites or exclusions beyond the missing-zones note.

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