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

Annotations already declare read-only, closed-world, idempotent and non-destructive, and the description reinforces determinism (same input, same output) plus concrete operational limits (64 KB input, 1 s per call, 1 MB result) that annotations cannot express. It does not describe the shape of the findings beyond 'lists scripts used', which the output schema covers. Minor wart: the stated 64 KB JSON input cap is smaller than the schema's maxLength of 262144, leaving a size ambiguity.

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?

Front-loaded with purpose, then When / Not for / Side effects / Deterministic / Limits in a scannable labeled structure. The Spanish and English halves are deliberate duplication for bilingual serving, but they do double the token cost.

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 need not be explained; the description covers the remaining agent needs: safety profile, determinism, and hard limits. The only gap is the size-cap mismatch between the description and the schema's maxLength.

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?

Only one parameter and schema description coverage is 100%, so the schema already carries the semantics; the description adds no format or content guidance for 'text' beyond size limits. This is the baseline case where the structured field does the work.

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 resource ('Señala palabras que mezclan alfabetos') and names the concrete phenomenon it detects (Latin/Cyrillic homoglyph spoofing), plus that it lists scripts used. The sibling text-invisible-scan is explicitly distinguished, so an agent can choose between them without opening either schema.

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?

Contains explicit 'Cuándo:' (exact transformation/comparison/measurement of text) and 'No para:' (invisible characters, routed to text-invisible-scan). Both the positive trigger and the exclusion with a named alternative are spelled out.

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