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

Annotations already declare readOnlyHint, idempotentHint, and a closed-world scope, so the safety profile is covered. The description adds genuine behavioral context by scoping coverage to 'US-listed companies Ryufin covers' and naming the returned fields, but it says nothing about result ordering, pagination, or what happens when the query matches nothing.

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 short sentences with zero filler; the scope and lookup keys are front-loaded and the return value is appended second. Nothing repeats the title or restates the tool name unnecessarily.

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 usefully compensates by listing return fields, and annotations carry the safety profile. However, the undocumented limit parameter and the absence of any routing guidance to sibling retrieval tools leave real gaps for a tool whose main role is to feed tickers into the other tools.

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 50%: 'query' is documented in the schema, and the description reinforces its accepted forms (ticker or company name). The 'limit' parameter (default 8, max 20) is undocumented in both the schema and the description, so the description does not compensate for the coverage gap.

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 states a specific verb and resource ('Find US-listed companies Ryufin covers') plus the lookup keys (ticker or company name), which is unambiguous. It does not, however, distinguish it from siblings like get_stock_overview or get_stock_answers, so an agent gets no help choosing among them.

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?

Usage is only implied: the wording suggests this is a discovery/lookup step for finding a ticker, but there is no explicit when-to-use, no when-not-to-use, and no named alternative among the five sibling tools. An agent has to infer that this is the entry point before calling get_stock_overview or get_company_news.

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