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

Annotations already mark readOnlyHint=true, and the description adds useful behavioral context: comparisons are per use-case and per-task, deltas are reported for specific metrics, and problems/bugs are categorized as fixed/new/persisting. It also discloses the non-obvious default behavior for the against parameter.

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 sentences with a clear front-loaded purpose, followed by parameter orientation and an explicit when-to-use trigger. Every sentence earns its place and there is no filler or redundant restatement.

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?

The description fully covers what the comparison includes, how to orient the parameters, and when to invoke the tool. Even without an output schema, it names the returned dimensions sufficiently for an agent to know what to expect.

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 schema already fully documents both parameters. The description restates the 'later round' guidance and the default behavior of against, adding clarity but no substantive new information beyond the schema.

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 opens with a specific verb and resource: 'Compares two rounds of the same UT' and enumerates the exact deltas covered (success-rate, duration, rating) plus bug movement categories. This clearly distinguishes it from other UT-related tools and removes ambiguity about what the tool does.

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?

'Use it when asked to compare rounds or see what changed across iterations' provides an explicit trigger, and the instruction to pass the later round as utId clarifies orientation. It does not explicitly name alternatives, but no sibling appears to offer the same comparison, so the guidance is clear enough.

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