Compare benchmark summaries between two commits

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

With no annotations provided, the description carries the full burden of behavioral disclosure. It thoroughly discloses what the tool reports: added/removed tests, pass/fail status changes, top N regressions/improvements for both execution-style and compile-style tests, and a generic fieldChanges section. It also explains that fieldChanges 'flattens and ranks every numeric field,' making the tool's behavior highly predictable.

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 long but every clause earns its place: core behavior, output sections, ranking explanation, filter semantics, and a usage hint. It is front-loaded with the main diff operation and avoids repetition of schema details.

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?

This is a complex 7-parameter tool with no output schema and no annotations, but the description explains the full comparison behavior, the sections returned, the ranking logic, filter options, and how to approach the results. Nothing essential for calling the tool correctly is missing.

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%, so the baseline is 3. The description adds useful cross-tool meaning by stating the optional filters are 'same as list_summaries' and by clarifying that baseSha/currentSha are short-shas and topN applies per regression/improvement category. It does not redefine every property, but it enriches the schema meaning enough for a bump.

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: 'Diff all matching benchmark rows... between a base and current commit short-sha.' It clearly states what is compared and describes the unique output sections, which distinguishes it from the list/get sibling tools.

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 clear context for when to use the tool and even provides an internal guidance hint: 'use fieldChanges as a first-pass scan... before drilling into a specific metric.' It also references list_summaries for filter semantics. However, it does not explicitly state when-not-to-use it or name an alternative tool.

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