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

With only readOnlyHint available from annotations, the description carries the auth burden and does it well: it discloses that a login session is required, that an API key is insufficient, and that a Proof account/authentication step is needed. It stops short of describing rate limits or response shape, hence not 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?

Front-loaded with the core purpose, then prerequisites, then alternatives. The ACCESS paragraph largely repeats the login instructions already given in the first paragraph, which is the only real redundancy, but the content still 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?

No output schema exists, and the description gives only a coarse sense of the return ('account details, plan and settings'). Given the zero-parameter, read-only nature and the thorough auth guidance, this is close to complete, with the return shape being the remaining soft spot.

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 takes zero parameters, so the baseline is 4. The description correctly avoids inventing parameter semantics and instead spends its words on auth context, which is the only caller-relevant input here.

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 ('Get the signed-in user's account details, plan and settings') and explicitly distinguishes itself from lookalike siblings (get_self_api_key, get_settings) by scoping to the signed-in user rather than the API key's own account.

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?

Names the prerequisite flow (start_login, then wait_for_login until success), states the negative condition (an API key alone cannot read this), and routes to the correct alternatives for the API-key case. Nothing about selection 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.