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

Annotations already declare readOnlyHint, idempotentHint, openWorldHint=false and destructiveHint=false, so restating 'read-only, no network, no stored state' adds little. The genuinely new information is the parsing tolerance (case-insensitive, padding and spaces optional), determinism and the operational limits (64 KB input, 1 s, 1 MB result), which are useful but the description spends half its behavioral budget duplicating annotation content.

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 the action, then When / Not for / Side effects / Deterministic / Limits in a scannable pattern. It is however presented twice, in Spanish and English, which roughly doubles length without adding information for an English-reading agent.

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 two-parameter decoder with an output schema already defining return values, the description covers direction, alternatives, tolerance rules and hard limits. Nothing an agent needs in order to call it correctly is missing.

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%, so both parameters are documented structurally and the 3 baseline applies. The description adds meaning the schema lacks: that the input is parsed case-insensitively with optional padding and spaces, and that output_encoding governs how decoded bytes are rendered.

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 (decode RFC 4648 Base32) plus the concrete output targets (UTF-8 text, hex, base64). It also names the sibling it is not (base32-encode), so an agent can distinguish it 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?

Explicit 'When' clause and explicit 'Not for' exclusion pointing at base32-encode as the alternative, covering both directions of conversion. Routing guidance is complete with no inference required.

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