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

Annotations already declare readOnlyHint, idempotentHint, and destructiveHint=false, so the safety profile is covered. The description adds genuinely new behavior: the return format is Markdown, the content is documentation rather than data, and an api_key is required. No contradictions with 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?

Two sentences plus a parenthetical; the resource and its contents are front-loaded before the usage advice and auth note. No filler, though the parenthetical auth note partially duplicates the schema's required field.

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 single-parameter documentation-retrieval tool with no output schema, the description supplies everything needed: what it returns, the format (Markdown), the topics covered, and the auth prerequisite. Nothing an agent needs to invoke it correctly is missing.

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 100% and the single param is documented there, so baseline is 3. The description adds provenance the schema lacks — the key is issued in the admin console (管理画面で発行したキー) — which helps the agent understand how to obtain it, nudging above baseline.

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 (返します/returns) and resource (avacast の組み込み方), and enumerates the exact contents: セッションの作り方, ブラウザ SDK, REST API エンドポイント, エラーコード. An agent can immediately tell this apart from the CRUD siblings like create_session or get_usage.

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 clear situational context: 「コードを書く前に一度読んでください」 tells the agent to consult this before writing code. It stops short of naming any alternative or stating when NOT to call it, but no sibling offers overlapping documentation, so the guidance is sufficient.

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