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

Beyond readOnlyHint=true, the description adds real behavioral context: results may include preferred/other share classes identifiable via isPreferredShare, dividend yield is forecast-based when a forecast exists and actual otherwise, and the call costs 10 tokens. The cost disclosure alone is notable rate-limit-style context that structured fields do not carry.

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 first sentence front-loads purpose and the filter-combination rule follows immediately. The bilingual restatement of the preferred-share point is somewhat redundant for one language's reader but mirrors the tool's documented bilingual style, and no sentence is 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 16-parameter tool with no output schema, the description never indicates what a result record contains or how sorting/default limits affect output. The cost and share-class notes are helpful, but an agent still lacks the return-shape context that an output schema would normally supply.

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 only 44%, so the description needs to compensate. It does add meaning for the *MoreThan/*LowerThan filter family and the dividend-yield definition, but says nothing about isEtf, limit, order, sortBy, or sector semantics, leaving several parameters relying solely on the sparse schema.

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?

"Screen Japanese listed companies by valuation, profitability and dividend criteria" gives a specific verb (screen) and resource (Japanese listed companies) plus the three screening dimensions. It implicitly distinguishes itself from list_stocks and get_rankings by being filter-based, though it never names those siblings explicitly.

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 explains how to use the filters ("Combine any of the *MoreThan / *LowerThan filters") and notes the preferred-share caveat, which is genuinely useful. It never states when to prefer this over run_screener_preset, list_stocks, or get_rankings, so the agent must infer the boundary.

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