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

Annotations already declare readOnlyHint, idempotentHint, destructiveHint=false, and openWorldHint=false. The description reinforces 'Reads only: nothing is written or saved' and adds meaningful behavioral context: a second lookup with card and translations returns them checked and marked as written by the AI. This goes beyond the structured safety profile.

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?

The description is front-loaded with what it returns and is appropriately sized for a complex tool, but sentences are dense and some ideas (e.g., the two-step validation) are interwoven. It is adequate but could be tightened without losing clarity.

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 carries the burden of explaining return content. It describes the main result (cards and translations), the fallback when no card exists (rules for the word and missing languages), and the two-step validation. Some terms like 'Koboshi's rules' remain slightly vague, but overall it is complete enough to call correctly.

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%, so the baseline is 3. The description adds value by explaining that card and translations are used in a second lookup to get checked results, and that learning_language is the language the word is written in. It clarifies the intended workflow for parameters that share the same names as return values.

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?

The description states a specific verb (returns) and resource (what Koboshi holds for a word plus translations), and explicitly distinguishes itself from save_word. An agent can tell this is a read-only lookup tool without opening the 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?

It names the key alternative (save_word) and the condition that selects this tool over it: 'save_word performs this lookup itself, so this tool is for looking a word up without keeping it.' It also explains the second-lookup pattern for filling in missing cards, leaving little to inference.

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