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

Annotations already declare readOnlyHint, idempotentHint, openWorldHint=false and destructiveHint=false, yet the description still adds real value: it spells out no side effects, no network, no stored state, determinism, and concrete limits (64 KB input, 1 s per call, 1 MB result) that annotations cannot express.

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 core statement and cleanly structured with When / Not for / Side effects / Deterministic / Limits labels. The full Spanish-then-English duplication doubles the length, which is a real cost even though each language block is disciplined.

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 small pure-function tool with an output schema, full annotation coverage and 100% parameter documentation, nothing an agent needs to invoke it correctly is missing; limits and determinism round out the operational picture.

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 the baseline would be 3, but the description adds meaning: it clarifies the RFC 4648 alphabet (A-Z, 2-7) and that the input may be text or hex bytes, which maps to the input_encoding enum, plus optional padding. It does not, however, discuss when to pick utf8 vs hex or padding=false.

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: encodes text or hex bytes as RFC 4648 Base32 (A-Z, 2-7) with optional padding, plus a concrete use case (TOTP secrets). It explicitly names the sibling it is not (base32-decode), 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?

Provides explicit routing: 'Not for: decoding RFC 4648 Base32 (base32-decode)' and a 'When:' clause about exact conversion. The only flaw is the reciprocal phrase 'convert to or from this encoding', which slightly blurs the encode-only boundary that the exclusion then corrects.

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