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

The annotations already establish readOnlyHint=true, destructiveHint=false and openWorldHint=true, so the safety profile is covered. The description adds two things annotations cannot: the result is scoped to the bearer's own subscription, and the account key is always masked in output – a meaningful privacy disclosure for an agent relaying results.

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 short sentences with the scope stated first and the output-masking caveat second. Nothing is padded, though the second sentence could have been spent resolving the account_id ambiguity instead of only the masking behavior.

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 return-value detail is legitimately out of scope. However, for a tool with a single undocumented required parameter and several adjacent siblings (usage_summary, get_plan, mrr_summary), the description leaves the account_id meaning and the routing decision under-explained.

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 description coverage is 0% and the sole required parameter account_id has no title or description beyond its name, so the description must compensate and does not. It never explains what account_id should be or why a required identifier is needed when the result is described as bearer-owned, leaving a real ambiguity.

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 and resource: returning the bearer's subscription lifecycle and current-period quota. That is concrete enough to separate it from list_plans or get_plan, though it does not explicitly name a sibling to contrast against.

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 – the agent can infer this is the tool for checking its own subscription state and quota. There is no explicit guidance on when to prefer usage_summary or get_plan instead, and no prerequisites are stated.

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