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

Annotations already declare readOnly, idempotent, non-destructive and closed-world, so the safety profile is covered; the description still adds genuinely new context: determinism (same input, same output) and concrete limits (64 KB JSON input, 1 s per call, 1 MB output). It repeats the annotation-backed 'no red, sin estado' point, which is minor waste but not a 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?

Front-loaded with the core action, then cleanly labeled sections (When / Not for / Side effects / Deterministic / Limits), so it scans well. The cost is the full Spanish-then-English duplication, which roughly doubles length without adding information for a single reader.

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?

Covers everything needed to invoke correctly: encoding, determinism, cost limits, and no side effects; an output schema exists so return-value explanation is rightly omitted. Minor inconsistency: the description caps JSON input at 64 KB while the schema allows maxLength 1048576 characters, which could confuse an agent near the boundary.

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%, so both optional enums and the required `data` field are already documented in the schema; the description only echoes that input may be text, hex or base64. It adds no extra semantics such as how hex input is validated or when base64url output is preferable. Baseline 3 applies.

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-512 digest (FIPS 180-4)') and immediately names the sibling it must not be confused with: hash-sha512-256. The agent can distinguish it from the ~20 other hash-* tools purely from the description.

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 labeled 'When' section (compare content, match a published checksum) and an explicit 'Not for' section pointing at hash-sha512-256. Both the positive selection criterion and the exclusion are spelled out, leaving nothing to inference.

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