list_billing_evn_by_period

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

With no annotations, the description carries full burden and excels. It discloses the tool's core constraint (one month per call) and provides a clear protocol for multi-month ranges (inform user, ask permission). It also mentions the ability to retrieve FOCUS v1.3 compliant output from another resource, which is a notable behavioral trait not evident from the schema.

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 description is concise—three sentences that front-load the purpose and key behavioral instructions. Every sentence adds value with no redundancy or unnecessary detail.

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?

Given no output schema, the description is incomplete regarding the return value structure. It refers to 'provisioning itemized data (EVN)' without specifying fields or format. The multi-month handling instructions are good, but details like pagination, limits, or typical response size are missing, leaving the agent with gaps.

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 coverage is 100%, so the baseline is 3. The description reinforces the constraint that period must be a single month, but adds no new semantic information beyond what the parameter descriptions already provide. The contract parameter's source (get_billing_profile) is already documented in the 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?

The description clearly states the tool retrieves provisioning itemized data (EVN) for a specific billing period, with the constraint of one month per call. Among siblings, it distinguishes itself from list_billing_evn (which likely lacks period filtering) and other billing tools by focusing on EVN data for a given period.

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?

The description provides explicit instructions for handling multi-month requests: calculate the number of calls, inform the user, and ask permission. It also mentions an alternative output format (FOCUS v1.3) via a resource. However, it does not explicitly compare to siblings like list_billing_invoices_by_period or list_billing_usage, leaving the agent to infer that this tool is for EVN data only.

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