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

Annotations already declare readOnlyHint/idempotentHint/destructiveHint=false and closed-world, and the description reinforces this with side-effect, determinism and limit statements (1 s per call, 1 MB result) plus what strict mode actually validates. That is real added context, but the limits sentence says "entrada JSON de hasta 64 KB" while the tool consumes TOON and the schema allows 262144 characters — an internal inconsistency that could mislead about size limits.

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?

The content is well front-loaded (what it does, then when/not-for, then effects and limits), but the Spanish block and the English block repeat the same information almost verbatim, roughly doubling length without adding decision-relevant detail.

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?

With an output schema present and rich annotations, the description still supplies the operational envelope (determinism, time and size limits) and the strict-mode contract, which is enough to call it correctly. The only gap is the contradictory 64 KB figure against the schema's 262144-character 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?

Schema description coverage is 100%, so the baseline is 3; the description earns a bump by explaining what strict mode checks (declared lengths, widths, indentation, duplicate keys) and that non-strict applies only the five spec §14.4 recoveries. The indent parameter's semantics are left entirely to the schema.

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 ("Decodifica un texto TOON ... a JSON") plus the spec version and the constructs handled (indentation objects, inline/list/tabular arrays, keyed tables, quoted strings, comments). It explicitly distinguishes itself from the sibling toon-encode, so an agent can route between the pair without opening a 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?

Provides an explicit "Cuándo" trigger (structured data that must be transformed, compared or checked exactly) and an explicit "No para" exclusion naming the alternative toon-encode for the reverse direction. Both the positive and negative cases are stated, 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.