a11y_diff

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

No annotations exist, so the description carries the full burden. It usefully discloses the return convention ('ok=false means a regression to review') and the dual input mode, but says nothing about limits on snapshot size, whether inputs must be produced by a11y_snapshot, or any failure/side-effect behavior.

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?

Two dense sentences, zero filler, with the core purpose and the diff contents front-loaded ahead of the ok=false convention. Every clause carries information.

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 does the right thing by explaining the ok=false return meaning. Combined with 100% schema coverage on both params, an agent can invoke it correctly; only the sibling-boundary (vs a11y_diff_urls) is left open.

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% and both parameter descriptions already state BEFORE/AFTER and 'inline JSON or path'. The description's input-mode sentence simply restates that, adding no new syntax or format detail, so the baseline 3 applies.

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?

Names a specific verb+resource ('Regression diff between two accessibility snapshots') and enumerates what the diff contains (added/removed/renamed interactives, focus-order changes), which is far more specific than the bare name. It does not, however, distinguish itself from the sibling a11y_diff_urls, which is the most likely confusion point.

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 parenthetical 'before/after a deploy' implies a regression-review use case, so usage is inferable. There is no explicit when-to-use-this-vs-a11y_diff_urls guidance and no stated prerequisite (e.g., that inputs must come from a11y_snapshot).

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