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

Annotations already declare readOnlyHint, idempotentHint, destructiveHint=false and openWorldHint=false, so 'no side effects / read-only / no network' mostly restates structured data. The description does add genuinely new behavior: determinism and operational limits (64 KB input, 1 s per call, 1 MB result). One flaw: the stated 64 KB input limit conflicts with the schema's 1 MB maxLength for `data`, which could mislead an agent into needlessly rejecting large inputs.

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?

Content is front-loaded and every clause (purpose, when, not-for, side effects, limits) carries information. However, the entire description is duplicated verbatim in Spanish and English, roughly doubling the token footprint for the same payload.

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, and the description covers determinism and resource limits. The input-size limit it advertises contradicts the schema and the encodings are left to the schema, so it is slightly incomplete for a hashing tool where encoding mismatches are the main failure mode.

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% and two parameters are enums, so the baseline is 3. The description only restates the output-length range (1–1024 bytes), which the schema already declares via min/max, and never mentions input_encoding or output_encoding, so it adds no real meaning beyond the schema.

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 precise verb + resource: computes SHAKE256 (FIPS 202) with a chosen output length of 1–1024 bytes. It immediately distinguishes itself from the closest sibling by naming hash-shake128 as the tool NOT to use, which is exactly the ambiguity an agent would face in a list of ~50 hash/checksum tools.

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 with concrete triggers (compare content, match a published checksum) and an explicit 'Not for:' clause routing to hash-shake128. This is the full when/when-not/alternative pattern; 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.