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

Annotations already establish readOnlyHint, idempotentHint, and destructiveHint=false, but the description adds real behavioral value beyond them: it discloses that other tools return full pages and account credits afterward, that it returns the plan and usage, and that it is free. It stops short of covering token lifetime, revocation, or what happens if sign-in fails.

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?

Front-loaded with the core action and effect, then the fallback paths. The x402 URL clause is dense but earn its place as an alternative channel; the account/credits contrast is stated twice in essence, which slightly inflates length.

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?

With no output schema and no parameters, the description covers everything an agent needs: what it does, its side effect on sibling tools, a summary of its return value, cost, and two alternatives for the no-account case. Nothing material 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?

There are zero input parameters, so the baseline of 4 applies; there is nothing for the description to disambiguate. The mention of email is directed at the sibling request_api_key, not at this tool's own inputs.

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 and resource (connect the user's gankdat account) plus the mechanism (OAuth sign-in prompt). It distinguishes itself from siblings by explaining the downstream effect (full pages + credits instead of preview) and names request_api_key as the alternative path.

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?

Explicit when-to-use and when-not-to-use: use this when a person can complete an OAuth sign-in; when no person is available, use request_api_key or the x402 pay-per-call endpoint. The alternative and its selecting condition are both named.

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