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

Annotations already declare readOnlyHint=true and destructiveHint=false, so safety is covered. The description adds genuinely non-derivable context: it is a deprecated alias retained for backward compatibility and, importantly, its return format differs from fetch — a behavioral trait the agent would otherwise not know. It stops short of saying how the format differs, keeping it from a 5.

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?

Three short sentences with no filler, and the critical fact (this is the legacy name, use fetch instead) is front-loaded. Slightly roundabout phrasing around the 'izakasu.jp' aside, but it earns its words.

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-param read tool with full schema coverage and annotations, the description covers deprecation status, the sibling alternative, and the divergent return format. The one remaining gap — what exactly the different return shape is — is minor but real given there is no output schema.

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?

Only one parameter at 100% schema coverage, so the schema already documents the url/path and its Japanese-language tolerance. The description adds no syntax, format, or constraint information beyond what the schema provides, making the baseline 3 appropriate.

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+resource (returns a page's body, like fetch) and distinguishes itself from the sibling fetch by noting it is the legacy name and returns a different shape. The framing is deprecation-first rather than purpose-first, which muddies it slightly, but an agent can still tell what it does and how it differs from fetch.

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?

Explicitly routes the agent: it exists for those already connected, and '新しく使うときは fetch を使ってください' names the alternative and the condition that selects it. Nothing is left to inference.

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