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

Annotations already declare readOnlyHint=true and destructiveHint=false, so the safety profile is covered. The description adds meaningful behavioral context: it's an external observation (not vendor official), returns a closed-vocabulary conclusion, and includes a critical requirement to relay the disclaimer and citation. This goes beyond the annotations and informs the agent of expected output semantics and user-facing obligations. It does not contradict annotations.

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 two sentences with zero fluff. The first sentence front-loads the purpose and output components, and the second sentence delivers a critical user-facing instruction. Every word earns its place; it is concise without sacrificing necessary detail.

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?

The description is largely complete for a read-only status tool with one parameter and no output schema. It specifies the return contents (conclusion sentence, time, state bar, maintenance) and the mandatory disclaimer relay. It does not detail the exact format of the state bar or error behavior, but these are minor gaps given the annotations and the simplicity of the tool. An agent can call it correctly and interpret the output sufficiently.

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 has 100% description coverage for the single required parameter 'slug', with an example. The tool description does not add any additional parameter semantics beyond what the schema already provides. Since the schema fully documents the parameter, a baseline of 3 is appropriate; no compensation is needed.

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: 'returns current operational status of one Japanese business system'. It clarifies the external third-party nature and distinguishes from vendor announcements, which helps differentiate from sibling tools like renkeimap_system_facts. The output components (conclusion sentence, last-observed time, state bar, maintenance) are enumerated, making the tool's purpose unambiguous.

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 clearly implies when to use it (when operational status is needed) and even clarifies that it's not the vendor's official announcement, which is a useful context. However, it does not explicitly name sibling tools or state when NOT to use this tool (e.g., when official status is required, use vendor API). The 'Always relay disclaimer' instruction is a usage requirement but not a selection guideline. With no explicit alternatives mentioned, the guidance is adequate but not fully explicit.

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