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

Annotations already cover readOnly/idempotent/destructive/closed-world, but the description adds non-obvious behavior: results are localized while the reviewed French source is distinct, and the response carries a URL that must be cited. That is real context beyond the annotations, though it doesn't say what happens for an unknown slug or a missing translation.

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?

Three short sentences, front-loaded with the core action before the localization caveat and the citation obligation. Dense but every sentence contributes; only the slightly compressed phrasing costs a point.

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?

With no output schema, the description does state the shape of the return (definition, meanings, cited sources, URL) and flags the reviewed-French-vs-translation distinction plus a mandatory citation, which are the non-obvious parts. The remaining gap is slug/locale handling, which is left to the schema.

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 0%, so the description carries the full burden for the two parameters. 'Localized' weakly implies the locale parameter and 'one card' implies slug, but the slug pattern/format and the twelve-value locale enum are never mentioned — an agent gets no help beyond the schema itself.

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 ('Read') and a specific resource ('one localized card definition, meanings and cited sources'), which cleanly separates it from list/catalog/draw siblings that operate on many cards or produce a draw. It stops short of naming the sibling it displaces, but the singular scope makes the distinction inferable.

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?

Usage is implied rather than stated: 'Read one ... card' signals a single-slug lookup versus the list/draw siblings, and 'Display translations are separate from the reviewed French source' functions as a caveat on when the localized output is authoritative. There is no explicit when-to-use/when-not or named alternative.

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