list_billing_utilization_by_period

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

No annotations provided, so description handles full burden. Discloses single-month call limit, response size constraint, and effect of top_n with group_by. Does not explicitly state authentication/permissions, but as a read operation that's acceptable. Adds value beyond basic read hint.

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?

Three sentences, front-loaded with purpose. Each sentence provides distinct value (behavior, procedure, optimization tips). Slightly dense third sentence but still clear.

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?

Covers key usage patterns, constraints, and reference to FOCUS v1.3. With 8 parameters and no output schema, description addresses response size and filtering strategies. Could mention typical response format but not critical for selection.

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 baseline is 3. Description adds significant context: period constraint, range handling, same compaction flags as sibling, and details about top_n + group_by interaction. Enhances schema without redundancy.

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?

Clearly states verb (get) and resource (per-resource utilization) with specific scope (billing period YYYY-MM). Differentiates from sibling list tools like list_billing_utilization by mentioning period constraint and referring to same compaction flags.

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?

Provides explicit instructions for multi-month ranges (calculate calls, ask permission). Gives advice on scoping to keep response under 25 KB. Lacks explicit comparison to when to use list_billing_utilization instead, but context is clear.

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