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

Annotations already declare readOnly/idempotent/openWorld/non-destructive, so safety is covered. The description adds genuinely new behavioral context: chronological ordering, the meaning of a registrar's first entry (archive start or first sale), and that prices are annual and USD-denominated. It does not discuss result size or pagination, keeping it below 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?

Three tight sentences with zero filler, front-loaded with what the tool returns, then scoping/ordering, then unit semantics. Every sentence carries information an agent needs.

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 no output schema, the description carries the return-value burden and does so reasonably: it explains the entry sequence and price units. It leaves out volume/shape of results (e.g., how many registrars are typically returned) and the dangling `currency` reference is unexplained.

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%, so both parameters are already documented; the description adds only the ordering guarantee and currency semantics. It references a `currency` field that is not a parameter in the schema, which adds mild ambiguity rather than clarity, so this stays at the baseline.

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 result (every recorded price change for one TLD) plus ordering (oldest first) and data source (GoMain's daily archive). An agent can distinguish this from compare_prices (cross-registrar comparison) and tld_info (static registry facts) without opening a 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?

Usage is only implied: the description explains what the data means once you call it, but never says when to reach for it over tld_info or compare_prices, nor any prerequisites. Adequate for an obvious lookup tool, but no explicit routing or exclusions.

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