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

Annotations already cover read-only, idempotent, non-destructive and closed-world, so the description correctly doesn't repeat those; instead it adds genuinely new behavior: unknown entity names are left as-is, determinism, and hard limits (64 KB input, 1 s, 1 MB result). The stated 64 KB input cap conflicts with the schema's maxLength of 1,048,576, which is an internal inconsistency worth flagging but not 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?

Internally well-structured with labeled sections (Cuándo / No para / Efectos secundarios / Determinista / Límites) and the purpose is front-loaded. However, the entire content is then duplicated verbatim in a second language plus a pointer sentence ('EN completo / full EN: inputSchema.description'), roughly doubling length without adding information.

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, fully annotated tool with an output schema, the description covers purpose, triggers, exclusion, edge-case behavior, determinism and resource limits — everything an agent needs to call it correctly and safely.

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% with its own description and an example, so the schema already does the heavy lifting. The description adds only the flavor of what input looks like (named and numeric references) and the unknown-name fallback; it doesn't address edge cases like double-escaped input or whether partially escaped text is fine.

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?

Opens with a specific verb+resource: decodes HTML character references, both numeric (é é) and ~100 named entities. It explicitly names html-escape as the thing it is NOT, so an agent can distinguish it from the sibling 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?

Has explicit 'Cuándo' with concrete triggers (URL, HTTP header, token, version string, IP range, HTML/Markdown documents) and an explicit 'No para' pointing to html-escape. Both when-to-use and the alternative are spelled out, leaving nothing to inference.

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