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

Annotations already declare readOnly/idempotent/non-destructive and closed-world, so the safety profile is covered. The description adds real value by disclosing that results are baselined against per-video OCR distributions and that the WCAG contrast check comes with 'applicability caveats' — but it is silent on the non-obvious corpus-threshold behavior implied by min_videos and allow_broaden.

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 with the primary action front-loaded and the optional contrast check second. No filler, though the semicolon-joined clauses pack multiple ideas that could be split for clarity.

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?

An output schema exists, so return values needn't be explained. But for a tool with a nested per-item schema plus a corpus-filter and broadening mechanism, the description leaves the caller guessing how baseline comparisons resolve when filters or min_videos exclude matches.

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 0%, so the description must compensate. It does partly: 'geometry and display time' maps to box/line_height_pct/in_ms/out_ms and 'optional color contrast' maps to foreground/background/large_text. However the entire filters object, min_videos, and allow_broaden go unmentioned in both schema and description.

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 concrete verb and resource: checking supplied text geometry and display time, and comparing size/reading demand/margins against per-video OCR distributions. This is specific enough to separate it from corpus-level siblings like corpus_stats or compare_to_reference, though it never explicitly names an alternative.

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 'supplied text' implies the caller brings items, but there is no explicit when-to-use, when-not-to-use, or named alternative among the ~34 siblings. An agent must infer that this is the per-item readability validator rather than a plan-critique or reference-comparison tool.

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