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

Annotations already declare readOnlyHint, idempotentHint and openWorldHint=false, so the safety profile is covered structurally. The description adds genuinely useful context beyond that: this lookup works even before the index is built, and the coverage branch reports record counts and last-updated timestamps.

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 dense sentences, front-loaded with the primary purpose (decode codes) followed by the secondary one (report coverage). Every clause earns its place and there is no filler.

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?

An output schema exists, so return values need not be described, and the description covers both invocation modes plus the pre-index availability. Only the `filter` parameter's behavior is left entirely to the schema, which is acceptable given the schema documents it.

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%, with the enum values and the filter semantics fully documented in the schema itself. The description restates the same vocabulary list already enumerated in the `topic` enum and says nothing about the `filter` parameter, so it adds little beyond the schema. 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?

States a specific dual purpose — decoding FCC ULS code vocabularies or reporting index coverage — and enumerates the exact vocabularies (radio services, license statuses, location types, antenna types, applicant types, operator classes). This clearly separates it from the find/get/search sibling tools, which operate on records rather than code lookups.

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?

'Decode FCC ULS codes used by the other tools' establishes the context (a helper for interpreting values returned by siblings), and 'Works before the index is built' signals a prerequisite-free availability window. No explicit when-not guidance or named alternative is given, but the usage context is clear.

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