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

With no annotations provided, the description carries the full burden of behavioral disclosure. It transparently reveals that despite the name 'get_word', there is no by-slug endpoint, so it performs a keyword search and filters for an exact slug match. It also states the None return case. This goes beyond a simple operational summary, though it doesn't mention any permissions, rate limits, or other side effects, which are likely irrelevant for this read-only lookup.

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 concise: three sentences, each earning its place. It front-loads the primary purpose, then covers edge behavior, implementation note, and alternative. No fluff or redundant text.

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 simple single-parameter lookup tool, the description covers purpose, exact-match behavior, the underlying search mechanism, the None return case, and the sibling alternative. An output schema exists to detail the return structure, so the description doesn't need to explain that. The tool is adequately specified for an agent to use it 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?

The input schema already fully describes the single parameter 'slug' with examples and 'exact word slug'. The description reiterates 'exact Jisho slug' but adds no new semantic detail beyond what the schema provides. With 100% schema coverage, the description does not need to compensate, so a baseline score of 3 is appropriate.

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 clearly states the tool's function: 'Look up a single word by its exact Jisho slug.' It uses a specific verb ('look up') and resource ('single word', 'exact Jisho slug'), and immediately distinguishes itself from the sibling tool 'search_words' by noting that fuzzy lookup should use that alternative.

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 description provides explicit usage guidance: it's for exact slug lookups, and explicitly directs users to 'search_words' for fuzzy lookup. It also clarifies the behavior when no exact match exists (returns None), helping the agent decide when to call this tool.

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

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

No annotations are provided, so the description carries full responsibility for behavioral disclosure. It does not state whether the tool performs a read-only operation, whether it accesses an external service, any rate limits, or error behavior. The only added behavioral context is that it supports Jisho filters, which is more about parameter usage than operational behavior.

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 succinct, with a clear first sentence stating the tool's purpose and a second sentence providing valuable examples. No redundant information is included, and it is front-loaded with the core purpose.

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 two-parameter search tool with a complete output schema, the description is largely adequate. It clearly communicates what the tool does and how to use the keyword parameter. The main gap is the lack of explicit comparison with the sibling tool get_word, which would help the agent choose between them in context.

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 baseline is 3. The description adds concrete examples of valid keyword values (e.g., '#jlpt-n5', '#verb', '水', 'water'), which enriches the schema's brief mention of 'filters and wildcards'. This helps the agent understand the flexibility of the keyword parameter beyond the structural definition.

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 clearly states the tool's function: 'Search Jisho.org for words matching a keyword.' It specifies the resource (Jisho.org), the action (search), and the payload (words matching a keyword). It also differentiates itself from the sibling tool get_word by focusing on search rather than retrieval of a specific word, and mentions support for a wide range of filters.

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 description explains that the tool supports all Jisho search filters and provides examples, implying it is the appropriate tool for flexible keyword-based search. However, it does not explicitly state when to use this tool over the sibling get_word, nor does it mention any exclusions or alternatives.

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