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

Goes well past the annotations: declares no network access and no stored state, determinism (same input → same output), Unicode letter preservation, and concrete limits (64 KB JSON input, 1 s per call, 1 MB result). These are exactly the operational facts an agent needs and none are derivable from the readOnlyHint/idempotentHint flags.

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 purpose, then cleanly labeled clauses (When / Not for / Side effects / Deterministic / Limits). The full Spanish-then-English duplication roughly doubles the length for any single reader, which is the main cost against 'every sentence earns its place'.

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 and annotations cover the safety profile, so the description need not explain return values. What remains — tokenization behavior, determinism, Unicode handling, size and time limits — is fully covered for a one-parameter pure function.

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% and the single parameter is documented, so the baseline is 3; the description adds real meaning by explaining how the input string is interpreted (split on spaces, punctuation, camelCase/acronym boundaries, Unicode preserved). Minor friction: the schema caps text at 4096 chars while the description cites a 64 KB JSON limit, which are different scopes but easy to conflate.

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 ('Convierte texto o un identificador a Train-Case') plus the tokenization rule used to produce it. It explicitly names the sibling it is not (case-detect), so an agent can distinguish it from at least one nearby tool without opening a 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 an explicit 'Cuándo'/'When' clause and an explicit 'No para'/'Not for' exclusion routing to case-detect. However, the closest confusable siblings (case-pascal, case-kebab, case-title, case-constant) are never mentioned, so the agent still has to infer why Train-Case rather than another casing tool.

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