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 nonetheless adds real context beyond them: no network, no stored state, determinism, and concrete limits (64 KB input, 1 s, 1 MB result). The only blemish is that the stated 64 KB input limit does not match the schema's maxLength of 16384 chars, a mild internal inconsistency rather than an annotation contradiction.

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 core conversion, then labeled sections (When / Not for / Side effects / Deterministic / Limits) that scan well. The full Spanish-plus-English duplication roughly doubles the length for identical content, which costs a point against strict conciseness.

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?

For a single-parameter, read-only, output-schema-backed tool, nothing an agent needs is missing: purpose, routing, side effects, determinism and hard limits are all stated, and return values are covered by the output schema.

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 100% with a single required 'text' string, so the schema already carries parameter meaning. The description adds only the implicit notion that the text is UTF-8, which is baseline-level value — the 3 baseline 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?

States a specific verb and resource ('Convierte texto UTF-8 a bytes binarios de 8 bits separados por espacios') and explicitly names the sibling it is not for ('binary-decode'). An agent can distinguish it from the many other encoders in the sibling list without opening any 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?

Uses explicit 'Cuándo'/'When' and 'No para'/'Not for' clauses naming the alternative (binary-decode) and the condition that selects it. This is the when-to-use / when-not / alternative pattern at full strength.

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