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

Goes well beyond the annotations: it discloses a negative guarantee ("never returns prices or payment details") and enumerates the two 409 failure modes with their exact codes and the conditions that trigger them, including the no-subscription-at-all case. The read-only/idempotent hints are already in annotations, but the error contract is genuinely additive.

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 purpose in the first line, then scoping and error detail. The opening sentence duplicates the title verbatim, which is mild waste, and the error clause is dense prose, but no sentence is off-topic.

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 parameters, no output schema, and annotations already covering the safety profile, the description carries the remaining burden well: it describes what the payload contains, what it deliberately excludes, its scope, and every documented failure path. Nothing needed to call it correctly is missing.

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 disambiguate and the baseline is 4. No parameter behavior is asserted in a way that could conflict with the empty schema.

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 resource set (organization plan, subscription status, current billing period, message/agent usage against limits), so an agent knows exactly what is returned. However, it never names or contrasts with the sibling list_usage_history, so the current-vs-historical distinction must be inferred.

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?

Scope guidance is present ("company-wide, whatever the key's agent list"), which implies this is the org-level snapshot rather than a key-scoped read. But there is no explicit when-to-use versus list_usage_history or any stated prerequisite, so routing 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.