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

Annotations already declare readOnlyHint/openWorldHint/idempotent/destructive, so the "side effects: none" sentence largely repeats structured data. The description does add genuinely new behavioral context: the z shorthand and delimiter tolerance, determinism, and hard limits (64 KB input, 1 s per call, 1 MB result) that the agent cannot infer elsewhere.

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?

Each individual language version is tight and front-loaded, but the full text is duplicated verbatim in Spanish and English, roughly doubling the token cost for a simple two-parameter codec. Nothing is wasted within a language, yet the overall payload is larger than necessary.

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. With purpose, exclusion, determinism, side-effect profile, and concrete size/time limits all present, an agent has everything required to call this correctly and to predict failure modes.

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 baseline is 3. The description goes slightly beyond the schema by explaining accepted Ascii85 variants (delimiters optional, z shorthand), which matters for formatting the `ascii85` argument, though it says nothing about `output_encoding` beyond what the enum already documents.

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 ("Decodifica Ascii85") and immediately qualifies the accepted input forms ("con o sin <~ ~>", z shorthand). It explicitly names the inverse sibling ascii85-encode, so an agent can distinguish the two 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?

Has an explicit "Cuándo/When" and a "No para/Not for" that routes encoding work to ascii85-encode. The only blemish is that the When clause says bytes must be converted "to or from" this encoding, which momentarily implies both directions; the Not-for line resolves it, so the guidance is clear but not perfectly airtight.

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