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

readOnlyHint=true already covers the safety profile, and the description adds real context beyond it: case-insensitive matching and the fact that all deck fields, including deck-specific extras, come back. It does not say what happens when the exact term is absent from the deck, which is the main remaining behavioral gap.

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?

Two sentences, zero preamble: the matching rule leads, then the return payload. The enumerated deck extras are dense but each item disambiguates what 'every field' means for a given deck.

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 describing returns and does so per deck family. What it omits is the failure mode — whether a missing term yields an empty result or an error — which matters for a lookup keyed on an exact string.

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% and the deck enum is documented as coming from list_decks, so baseline is 3. The description goes further by explaining what 'term' can physically be (kanji, hanzi, jamo, word) and that matching is case-insensitive — meaning the schema alone would not supply.

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?

Names a specific verb+resource (fetch one deck entry) and pins the matching rule: exact term, case-insensitive, where the term may be a kanji, hanzi, jamo, or word. This implicitly separates it from search_deck, which an agent can infer handles non-exact lookup.

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 exact-match requirement implies when this tool applies (you already know the term), but the description never names search_deck or states an exclusion such as 'use search_deck when you only have a partial string or a meaning'. Usage must be inferred.

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