Read OAuth identity

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

Annotations already cover read-only, idempotent, non-destructive and open-world traits. The description adds value beyond them: it is a single fixed request, it will not refresh tokens, and it rejects API keys — real behavioral constraints not present in the 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 tightly packed sentences with zero filler; the core action and the credential requirement are both front-loaded.

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 simple no-argument read, the description covers invocation constraints (auth type, no fallback, no refresh) adequately. With no output schema, it says nothing about what UserInfo fields come back, which is the one remaining gap.

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 optional 'account' param is fully documented in the schema. The description gestures at 'explicitly selected' account/token but adds no syntax or format detail beyond the schema, so baseline 3 is 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?

The description names a specific verb (GET) and resource (UserInfo) and constrains the credential type to an 'externally minted OAuth access token.' It is clear on what the tool does, but does not differentiate it from any sibling (which are Mailchimp-style subscriber/campaign tools), leaving the agent to infer placement from the name alone.

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?

'API keys refuse; no refresh, OAuth login or fallback' is an explicit when-not condition, telling the agent this only works with a pre-minted OAuth token and that there is no alternative auth path. It stops short of naming an alternative tool to use instead, but the credential precondition is stated plainly.

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