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

Annotations already declare readOnlyHint=true, idempotentHint=true, openWorldHint=false, and destructiveHint=false, so the safety profile is fully covered. The description's value-add is scope: results come from the authenticated customer and cannot be targeted at another account. It does not, however, mention behavior when unauthenticated or whether calling it consumes quota (relevant given it reports rate limits).

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?

One sentence, front-loaded with the verb and the returned fields, with no filler. Every clause names a distinct piece of returned data, and nothing is repeated from the annotations.

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?

An output schema exists, so the description does not need to explain return values, and with no parameters the schema is trivially complete. The remaining minor gap is error/auth-failure behavior, which is not addressed, but for a zero-argument read tool the description covers what an agent needs to select and call it.

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 parameters, so per the baseline the schema carries no semantics to compensate for. The description correctly implies the tool is argument-free and implicitly scoped to the caller's identity, which is the only parameter-like distinction that matters 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?

The description uses a specific verb ('Return') and enumerates the exact resources returned: plan, credits, rate limit, and usage totals. It is scoped to 'the authenticated customer,' which immediately tells an agent whose data this is. Sibling tools (research, get_video, search_insights) are unrelated, so no sibling differentiation is required, but the description also doesn't need to name an alternative.

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 only implied: an agent can infer this is the tool for checking account status, credits, and limits, but there is no explicit when-to-use statement, no prerequisites, and no exclusions. Because the tool takes no parameters and is read-only, the ambiguity is small, but the description does not actively route the agent.

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