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

Goes well beyond the annotations (destructive/idempotent hints) by disclosing the temporal effect ('counts as known for about a month'), the concrete follow-up behavior ('quizzes of that type skip the word and check it once in about three weeks'), the terminal state ('all five make the word "known" and it leaves review'), and the reversal path ('can be removed in the word card in the app'). This is exactly the extra context the annotations cannot convey.

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?

Appropriately sized for a tool with this much implicit behavior, and the core action is front-loaded before the skill/effect details. The skill enumeration with nested parentheticals ('recognize (understands: translates from the language being learned)') is dense and slightly hard to parse, but no sentence is filler.

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?

There is no output schema, and the description still covers purpose, per-skill semantics, duration, side effects on quizzes/review, removal, and the key sibling distinction. Edge behavior (combining terms and card_ids, exact return) is left implicit, which keeps it just short of fully complete.

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?

With 0% schema description coverage the description carries the param burden and does so well: it enumerates all five valid skills with parenthetical meanings, states that empty means all five, defines terms as vocabulary phrases with a shared 200-item cap, and labels card_ids as cards. It doesn't specify formats/ID shapes, so it is strong but not exhaustive.

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 action on a specific resource: marking phrases the user already knows as 'known'. It also explicitly differentiates itself from the sibling skip_card ('Not the same as skip_card, don't learn at all'), so an agent can pick the right tool without opening either 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?

Gives a clear when-not via the skip_card contrast and explains the per-skill consequences that select it (e.g. 'use means the word will not become a conversation target'). It does not discuss other alternatives such as defer_card or srs_review, so it stops short of full when/when-not coverage.

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