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

Annotations already declare readOnly, openWorld, idempotent, and non-destructive hints. The description adds substantial behavioral detail beyond that: it defines the comparison baseline, includes domain matching (www.<domain> and subdomains), alphabetical ordering, limit caps, offset semantics, and response navigation via hasMore/nextOffset. This is rich, non-obvious behavior that an agent needs to know.

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?

The description is three dense sentences, front-loaded with the core purpose, then covering the critical input constraint, domain behavior, pagination, and the value proposition. Every sentence earns its place, with no filler or repetition.

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?

For a tool with four optional params, XOR constraints, and pagination but no output schema, the description covers the key input semantics and response navigation. It mentions per-category deltas and hasMore/nextOffset, though it does not describe the exact shape of those deltas, which slightly limits completeness.

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 the baseline is 3. The description adds value by clarifying the XOR relationship between url and domain, explicitly stating that offset is a row skipper, not a page number, and explaining that offset is ignored in single-URL mode. This goes beyond the schema descriptions.

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 states a specific operation: compare the oldest baseline against the latest non-expired test for a URL or domain, with pre-computed per-category deltas. This clearly distinguishes it from sibling history tools like gvt_get_latest, gvt_get_oldest, and gvt_get_test_results by emphasizing the comparison and delta computation.

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 description gives explicit usage constraints: provide exactly one of url or domain, explains domain matching scope, and defines offset-based pagination. It also frames this as a replacement for paging full history and computing comparisons client-side. It does not explicitly name sibling alternatives, but the context is clear enough for correct selection.

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