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

Annotations already declare readOnlyHint=true, idempotentHint=true, destructiveHint=false, covering safety. The description adds the return contents and the troubleshooting purpose, which is beyond annotation coverage. No contradiction. It doesn't disclose pagination or rate limits, but those are minor given the read-only nature.

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 concise sentences, front-loaded with the core function and return data, followed by the use case. No wasted words; the api_key note is brief and relevant.

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 read-only list tool with a simple output (status, end reason, connection seconds), the description is sufficient. It specifies the max count and the key use case. It lacks exact output formatting or pagination details, but these are not critical given the tool's simplicity and the annotations covering safety.

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 description coverage is 100%, with both limit and api_key fully documented (default, max, format). The description's mention of max 50 mirrors the schema's limit max. It adds no additional parameter semantics beyond what the schema already provides, so baseline 3 applies.

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 ('返します' – returns) and resource ('直近のセッション' – recent sessions), and specifies the returned data (状態・終了理由・接続秒数). It clearly distinguishes from siblings like get_session (single session) and end_session (mutation).

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 gives a concrete use case: troubleshooting connectivity issues ('繋がらない・すぐ切れる問題の切り分けに使います'). It doesn't explicitly mention alternatives or when not to use, but the context is clear and relevant.

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