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

Annotations already declare readOnly, idempotent, non-destructive and closed-world, and the description reinforces this with 'no network access, no stored state' plus determinism and concrete limits (64 KB input, 1 s per call, 1 MB result) — genuinely additive runtime context. Minor discrepancy: the schema allows maxLength 1,048,576 for 'encoded' while the description caps JSON input at 64 KB.

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?

Purpose, exclusions, side effects and limits are front-loaded in a scannable structure. However, the entire block is duplicated verbatim in Spanish and English, roughly doubling 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?

An output schema exists, so return values need not be explained, and the description covers determinism, side effects, limits and the encoding alternative. Only the partial enumeration of output_encoding options and the input-size discrepancy leave small gaps.

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 an enum, default and example for both parameters, so the baseline applies. The description only mentions UTF-8 and hex outputs, omitting the base64 option that the enum provides, so it adds no param-level 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 specific verb and resource ('Decodes MIME quoted-printable (RFC 2045)... to UTF-8 text or hex'), including the RFC and the removal of soft line breaks. It explicitly names the mirror sibling quoted-printable-encode as the tool it is not, so an agent can distinguish the pair 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?

The 'When' and 'Not for' clauses give a real routing rule and name the exact alternative (quoted-printable-encode). The phrasing 'converted to or from this encoding' is slightly muddled for a decode-only tool, since the reverse direction belongs to the sibling, which weakens the guidance a bit.

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