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

Annotations already mark the tool as read-only, idempotent, and non-destructive. The description adds meaningful behavioral context beyond that: registration must be performed by the user personally with Google or GitHub, the agent cannot proxy the registration, and the API key issued later should be passed to future tools. This is genuinely useful operational information.

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 with no filler. The primary result is front-loaded in the first sentence, and the second sentence carries the key constraints and follow-up instruction. Every clause earns its place.

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 zero-parameter, read-only informational tool with no output schema, the description is complete: it says what is returned, who must perform the registration, why the agent cannot do it, and what to do after registration. Nothing an agent needs in order to use this tool 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?

The tool has zero parameters and the schema covers this fully, so the baseline is 4. The description adds value by explaining that the API key obtained after registration should be used as the api_key argument for subsequent tools, which clarifies the workflow without needing any parameter documentation.

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: 'SealGate の登録 URL を返します' (returns the SealGate signup URL). It clearly distinguishes itself from the sibling tools, none of which handle registration, and the title reinforces the purpose without being the only source.

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 tells when to use the tool: when the user needs to register for SealGate. It also provides an important exclusion: the agent cannot register on the user's behalf, so the tool should only be used to give the user the signup URL. It does not name an alternative tool, but no closer alternative exists among the siblings.

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