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

Annotations already declare readOnlyHint=true, idempotentHint=true, destructiveHint=false, and openWorldHint=false, so the safety profile is fully covered structurally. The description adds nothing beyond that—no note on what the response contains (a list of months? in what format?), no pagination or scope remarks—so it earns little credit on top of 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?

The first sentence is duplicated verbatim, and the operation ID is noise for an agent. No value-bearing content is front-loaded; the text is short only because it says almost nothing.

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, no parameter documentation, and a nested free-form query object, the description would need to explain the return shape and filtering behavior. It instead defers entirely to describe_operation, leaving an agent unable to invoke the tool correctly without a second call.

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% with two free-form objects (query, params) whose contents are entirely undocumented. The description provides no parameter meaning at all, only a generic referral to describe_operation, so it does not compensate for the coverage gap.

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 simply restates the HTTP path 'GET /api/billing/available-months' twice, which is the title rather than an explanation of what the endpoint returns or is used for. An agent can infer it lists billing months, but nothing confirms that beyond the URL text, and there is no differentiation from the many sibling billing/subscription endpoints (e.g., get_billing_projected, get_subscription_billing_check).

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?

There is no statement of when to call this versus alternatives such as get_billing_projected or the subscription usage tools. The only actionable hint is the pointer to describe_operation for native request schemas, which is a discovery step rather than usage guidance.

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