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

Annotations only declare readOnlyHint=true; the description adds genuine context beyond that by disclosing the auth requirement (agent token) and the sensitivity/contents of the payload (acting-for identity, scopes, limits, daily spend). It does not mention rate limits or whether results are cached, keeping it short of 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?

Two tight sentences, zero waste: the returned data is front-loaded and the auth constraint follows as a qualifier. Every clause carries information.

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, the description compensates by enumerating the returned fields (principal, scopes, limits, spend today) and the auth precondition. It is close to sufficient for a zero-parameter read tool, though it says nothing about the response shape or error behavior when the token is missing or expired.

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 there is nothing for the description to clarify; the 4 baseline applies. The description correctly implies a no-argument call gated only by the agent token.

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 the specific resource it returns — the acting principal, its scopes, limits, and today's spend — which is unmistakably the identity/self-inspection tool among siblings that all deal with tasks, services, and messages. It stops short of explicitly contrasting itself with any sibling, but no sibling overlaps this purpose.

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?

Usage is implied (call this to learn who you act for, what you may do, and your budget) and the auth prerequisite 'Requires an agent token' is stated. There is no explicit when-to-use or when-not-to-use guidance and no named alternative.

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