verify_build

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

Annotations already declare the safety profile (readOnlyHint=true, destructiveHint=false, openWorldHint=true), so the bar is lower. The description usefully adds the output shape (pass/warn/fail verdict with evidence lines) and the two analysis methods, but it ignores the notable idempotentHint=false, giving no signal about non-determinism or the cost/latency of fetching and rendering two live URLs.

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, front-loaded with the core action and result type, with no filler. The closing 'Closes the design loop' line is mildly promotional but earns some of its place by conveying workflow context.

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?

There is no output schema, and the description compensates by naming the return artifacts (verdict plus evidence lines) and the comparison basis. Combined with annotations covering safety and network scope, it is nearly complete; only the failure/non-idempotency behavior remains unaddressed.

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 75% and the schema already documents buildUrl, referenceUrl and the viewport default with concrete dimensions. The description names the reference concept but adds no syntax, precedence, or guidance for waitStrategy, which the schema leaves entirely bare. Baseline 3 is appropriate.

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?

States a specific verb and two resources ('compare a built site against a reference') and concretizes the comparison dimensions (band-structure match + motion fingerprint). It does not, however, distinguish itself from the sibling 'compare_sites', leaving a plausible ambiguity for an agent picking between the two.

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 phrase 'Closes the design loop: build → verify → fix → re-verify' implies the workflow position, and the examples (Awwwards winner, client's old site) hint at likely scenarios. But it never states when NOT to use it or which sibling (e.g. compare_sites, analyze_page_structure) covers adjacent needs, so the routing is left to inference.

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