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

Annotations already declare readOnlyHint and idempotentHint, so the description does not need to restate safety. It does add genuinely useful behavior beyond the annotations: no traditional/simplified or variant folding, strict exact-match input, and an explicit null sentinel when the character is not in the database. The only remaining gap is nothing about result shape or caching, which the output schema largely covers.

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?

Front-loads the core capability and returned fields, then the strictness constraints, then the sibling routing in a single compact closing clause. Every phrase carries information; no filler or redundancy despite covering four separate concerns.

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 single-parameter read tool with full schema coverage, an output schema, and read-only/idempotent annotations, nothing an agent needs is missing. Input strictness, miss behavior, and tool routing are all covered, so the description is proportionate to the tool's complexity.

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% with a documented 'char' property, so the baseline is 3. The description adds real constraint semantics the schema does not express — exact-match only, no variant folding, no whitespace forms, and null-on-miss — which meaningfully changes how an agent should format input and interpret a missing result.

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+resource (query the naming character database by exact single character) and enumerates exactly what facts are returned (frequency, five elements, strokes, radical, pinyin, tone). It explicitly separates itself from sibling tools by stating it handles only single characters, not pools, composition, or full-name evaluation.

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 an explicit when-to-use statement (verifying single-character attributes) plus a named alternative for each adjacent task: naming_pick for the character pool, naming_compose for candidate names, naming_check for whole-name evaluation. Exclusions are also given (no multi-character or whitespace variants).

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