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

Annotations already declare this as a read-only, idempotent, non-destructive, closed-world list operation. The description adds meaningful behavioral context: every tester count must include its source and date, joining a test requires website signup, and remaining deposited credits are not a tester cap. Return ordering/pagination is not covered, but the core behaviors are well disclosed.

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 front-loaded with purpose, then usage, then behavioral caveats. The bilingual Japanese/English duplication slightly weakens conciseness, and the English version omits one caveat present in Japanese, but the information remains reasonably tight.

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 no-parameter, read-only list tool with annotations covering safety, the description supplies the important missing context: what the list represents, when to use it, how to relay tester counts, and the signup prerequisite. It does not fully specify pagination or complete return structure, but no output schema exists and the essential agent-facing context is present.

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 tool has zero parameters, so the baseline is 4. No parameter-level semantics are needed beyond the description of what the returned list contains.

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 and resource: returns a list of apps currently recruiting testers on Minna no Tester. It is clear enough that an agent can distinguish this from service-info or opt-in-link tools, though it does not explicitly name those siblings as alternatives.

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 explicit usage context: use when the user asks which apps they can test now or wants to participate as a tester. It lacks when-not guidance or direct references to sibling tools, but the intended trigger is clear.

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