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

Annotations already cover read-only, idempotent, closed-world and non-destructive, yet the description still adds real context: resource limits (64 KB JSON input, 1 s per call, 1 MB result) and the caveat that output bytes may differ across zlib versions while decompression remains compatible. Some phrases ("sin red, sin estado guardado") merely restate the annotations, and the "Determinista" claim sits slightly at odds with the version-variance note, keeping this short of a 5.

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 front-loaded: purpose first, then when/when-not, side effects and limits in labelled clauses. The only inefficiency is the duplicated full Spanish and English rendering of the same content, which inflates length without adding information.

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 4-parameter, output-schema-bearing compression tool, everything an agent needs is present: scope, the sibling to avoid, safety profile, resource limits and the version-compatibility caveat. Return values are covered by the output schema, so no explanation of the response shape is required.

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 both enums (format, input_encoding) are documented with defaults in the schema, so the baseline is 3. The description mentions text/bytes and format names but adds nothing about the `level` parameter or how `input_encoding` should be paired with `data`, so it does not enrich parameter 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 concrete verb (compress), the exact resource (text or bytes) and enumerates the supported codings with their RFCs (gzip RFC 1952, zlib/deflate RFC 1950/1951, Brotli RFC 7932), plus what it returns (base64, sizes, ratio). It also names the complementary sibling zlib-decompress, so an agent can separate the two without inspecting 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 routing is given in both directions: "Cuándo: hay que convertir bytes o texto a esta codificación... sin adivinar" and "No para: descomprimir datos base64 en gzip, zlib/deflate, deflate sin cabecera o Brotli (zlib-decompress)". The exclusion names the exact alternative tool and the condition that selects it.

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