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

Annotations already declare readOnlyHint, idempotentHint, and openWorldHint=false, but the description adds operationally useful context beyond them: no side effects, no stored state, determinism, and concrete limits (64 KB JSON input, 1 s per call, 1 MB result). These are things the agent cannot infer from annotations.

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 purpose, then when/not-for, side effects, determinism, and limits in a clean order. The full text is duplicated in Spanish and English, which doubles length for the same content, though the structure itself is tight.

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, annotations covering the safety profile, and both parameters documented in schema plus description, an agent has everything needed to invoke this correctly. The only omission (base64 output) is already visible in the enum.

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%, but the description adds real meaning the schema does not: spaces are optional in the bit string and length must be a multiple of 8. Minor gap: it says output is 'text UTF-8 or hex' while the schema enum also permits base64, so the output_encoding option is under-described.

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 bits 0/1 a texto UTF-8') and explicitly names the sibling it is not: binary-encode. An agent can distinguish the two directions of the binary conversion 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?

Provides an explicit 'Cuándo' section describing the situation that selects this tool, plus a 'No para' clause naming binary-encode as the alternative for the opposite direction. Nothing is left to inference.

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