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

Annotations already declare readOnlyHint=true, idempotentHint=true, and destructiveHint=false, so the safety profile is established. The description adds valuable behavioral context about accepted authentication methods (API token or Bearer web session) and clarifies that the agent should leverage an existing session. It doesn't describe return formatting, but the read-only, idempotent nature is well covered.

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 compact and front-loaded with the core purpose. The authentication caveat and action list are essential and are stated without redundancy. Every clause contributes necessary information for correct invocation.

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?

The description covers the main invocation details: authentication, action selection, and optional date range. Since there is no output schema, it doesn't explain return values, but the action names are fairly self-explanatory. It is reasonably complete for a read-only reporting tool, though per-action output specifics are not detailed.

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 100%, so the baseline is 3. The description adds semantic value by explaining that an approved Bearer web session is accepted as an alternative to an sk_ token and by reinforcing the YYYY-MM-DD format for dates. This goes slightly beyond the schema's parameter notes.

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 identifies the tool as 'Revenue and traffic reporting for your account' and enumerates specific action modes (overview, earnings_history, epmv_trend, etc.), making its purpose concrete. This distinguishes it from sibling tools like payments, account, or subscriptions, which cover different financial/account functions.

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?

It provides clear context: the tool is for revenue/traffic reporting and should be invoked with an action plus optional date range. It also gives explicit authentication guidance, including not asking for an sk_ token when a working web session exists. It does not explicitly discuss alternatives or exclusions among siblings, but the domain is clear enough.

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