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

Goes well beyond the annotations by disclosing concrete limits (64 KB JSON input, 1 s per call, 1 MB output), determinism, and the 'z for zero groups' variant behavior — all operationally relevant. The 'no side effects / no network / no stored state' sentence largely restates readOnlyHint, openWorldHint and destructiveHint, which keeps this from a 5.

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 language version is tightly front-loaded (variant first, then when/not-for, then side effects, limits), which is good structure. However, the description duplicates the entire content verbatim in Spanish and English, 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 pure-function encoder with an output schema and full annotation coverage, everything needed to invoke it correctly is present: variant semantics, delimiter behavior, input limits and determinism. Return values are covered by the output schema, so no gap remains.

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 data, delimiters and input_encoding are already fully documented in the schema, making 3 the baseline. The description adds only the meaning of the <~ ~> wrapper and the Adobe/z behavior, and says nothing about when to pick input_encoding=hex versus utf8.

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 plus the exact variant: 'Codifica bytes en Ascii85 (variante Adobe)' and in EN clarifies 'Adobe/btoa variant, z for zero groups'. The agent can immediately distinguish it from ascii85-decode and from base64/hex siblings because both the resource and the flavor of Ascii85 are named.

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?

Gives an explicit 'Cuándo' (convert bytes/text to or from this encoding, exactly) and an explicit 'No para: decodificar Ascii85 (ascii85-decode)' that names the alternative tool. The only flaw is the phrase 'o desde ella' (or from it), which hints at round-tripping and slightly muddies the otherwise clean encode-vs-decode boundary.

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