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

readOnlyHint already certifies a safe read. The description adds meaningful behavioral detail: substring matching spans term/reading/meanings/category, category is exact, difficulty maps to kanji school grade, and results paginate via offset. It stops short of describing result ordering or return fields.

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 compact sentences, front-loaded with the action and matching semantics; the examples are purposeful and no sentence restates the schema unnecessarily. There is zero 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?

For a six-parameter read-only search with full schema coverage, the description gives enough to call it correctly: deck scope, query matching, filters, and paging. It does not describe result shape or ordering, which is a minor gap because no output schema exists.

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%, so the schema already documents all six parameters and the baseline would be 3. The description earns extra credit by expanding query semantics with examples, clarifying category is exact and sourced from list_decks, and explaining difficulty's deck-specific meaning. It adds little for limit/offset beyond the schema, but enough for a 4.

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 'Search one deck' and immediately defines what the query matches (term, reading, meanings, category), with concrete examples. This is a specific verb+resource, and the one-deck search scope distinguishes it from siblings like list_decks and get_entry.

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 implied use case is searching within a single deck, and it explains how to narrow with category/difficulty and page with offset. However, it never explicitly states when to use this instead of list_decks or get_entry, nor any when-not conditions.

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