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

Annotations already declare readOnlyHint, idempotentHint, openWorldHint=false and destructiveHint=false, so the restated 'no side effects, no network, no stored state' is partly redundant. The description does add genuinely new operational context beyond annotations: determinism, a 64 KB JSON input cap, 1 s per call, and a 1 MB result cap.

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 the definition, then labeled clauses for when/not-for/effects/limits, which is easy to scan. It is somewhat long because the entire content is duplicated in Spanish and English, costing some density but not 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 need no explanation; the description still covers the input constraint (equal length), the mode semantics, side effects, determinism and quotas. Nothing an agent needs to invoke this 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 coverage is 100%, so parameters are already documented; the description adds the non-obvious constraint that the two strings must be of equal length and explains what 'hex_bits' means at the bit level. That meaning is not in the schema and prevents a common misuse.

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+resource: counting differing positions between two equal-length strings, and clarifies the two comparison granularities (code points vs hex bits). It also names the sibling it must not be confused with, so an agent can discriminate without opening schemas.

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?

Explicit 'Cuándo' section gives the selecting condition (exact transform/compare/measure rather than approximate) and an explicit 'No para' exclusion pointing to levenshtein-distance. Both when-to-use and when-not are present with a named alternative.

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