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

Annotations already declare read-only, idempotent, closed-world and non-destructive, yet the description still adds useful traits: no network, no stored state, determinism, and per-call limits (64 KB JSON, 1 s, 1 MB result). One caveat: the stated 64 KB input cap conflicts with the schema's maxLength of 1048576, a mild inconsistency rather than an annotation contradiction.

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?

Well structured and front-loaded: purpose, when, not-for, side effects, determinism, limits. The cost is full Spanish/English duplication, which roughly doubles the token footprint for identical content in a toolset where most siblings carry only one language.

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 not be explained; the description still covers scope, alternatives, safety profile and operational limits. For a single-input digest tool, an agent has everything required to call it correctly.

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% with enum values and defaults documented for input_encoding and output_encoding, so the baseline is 3. The description mentions the three input encodings but adds nothing about output encoding choices or how `data` is interpreted per encoding beyond what the schema already states.

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 (computes the SHA-384 digest) plus the governing standard FIPS 180-4, and immediately scopes the input domain (text, hex or base64). It names the nearest sibling, hash-sha512, so an agent can route between similarly named hash tools without opening schemas.

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 gives concrete selection criteria (compare content, match a published checksum) and an explicit "No para / Not for" clause naming hash-sha512 as the alternative. Nothing about tool choice 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.