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

Annotations already declare readOnlyHint=true, destructiveHint=false, idempotentHint=true. The description adds that the tool is free ('Free, no charge (APIbase)'), which is behavioral cost information. It also clarifies period-granularity constraints. No contradictions with 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 description is three sentences, each earning its place: purpose, visualization hint, and granularity guidance. It is front-loaded with the core action. Minor improvement could merge the visualization sentence into the first.

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 the tool's simplicity (2 params, no required), annotations, and output schema, the description covers key aspects: data types, granularity rules, and cost. It does not mention output format, but the output schema likely handles that. Sibling tools exist, but the description is sufficient for distinguishing.

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?

Input schema has 100% description coverage with enum values and defaults. The description adds context: 'hourly (for 1d period) or daily (for 7d/30d)', which clarifies the relationship between period and granularity beyond the schema's individual descriptions.

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 'Get time-series usage data — calls, cost, cache hits per hour or day over a period', providing a specific verb and resource. It distinguishes from sibling tools like account.analytics.usage (general usage) and account.analytics.tools (list of tools) by focusing on granular time-series data.

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 gives explicit guidance: 'Choose granularity: hourly (for 1d period) or daily (for 7d/30d)'. This tells the agent when to use each granularity based on period. It also mentions 'Free, no charge' which is useful context. However, it does not explicitly say when not to use this tool or mention alternatives.

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