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

Annotations already declare readOnlyHint, idempotentHint, and non-destructive behavior, so the description correctly avoids repeating those. It adds valuable behavioral context by explaining the classification output and the default behavior when run ids are omitted.

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 concise sentences with no wasted words. The core purpose is front-loaded, followed by the output detail and the default usage hint—all in a logical order.

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 4-parameter tool with no output schema, the description conveys the essential behavior: comparison of metrics, classification of results, and default run selection. It covers the key aspects an agent needs to invoke it correctly, though it doesn't detail response structure or error handling—minor gaps given the tool's simplicity.

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 only 25% (only path has a description), yet the description clarifies the meaning of run ids (toRunId, fromRunId) by explaining their optionality and default behavior, and implicitly defines 'tool' by referencing 'a tool'. This compensates well for the sparse 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?

Description clearly states a specific verb (compare) and resource (recorded runs) with the additional detail that it classifies each metric as better, worse, or unchanged. This distinguishes it from sibling tools like list_reports or audit_360.

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?

Provides explicit guidance on omitting run ids to default to the two most recent runs, and frames the use case as proving codebase improvement. While it doesn't name alternative tools or exclusions, the purpose is distinct enough that an agent can infer when to use it.

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