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

Annotations already declare readOnlyHint=true and destructiveHint=false, so the safety profile is covered. The description adds that the report is a spending breakdown across three dimensions, which is useful context, but says nothing about date-range defaults, pagination, or response shape for a report tool.

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?

Two tight sentences, no waste, with the core purpose front-loaded before the usage hint. Minor gap: it could be compressed further or structured as purpose-then-when.

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?

For a read-only report tool with full schema coverage and no output schema, the description is nearly sufficient: it names the tool's function and the report's breakdown dimensions. The main residual gap is that it doesn't describe the returned report structure, which matters somewhat given no output schema exists.

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 all three parameters (from, to, auth_token) are already documented in the schema, including the auth fallback precedence. The description adds the aggregation dimensions (service, period, transaction type) but no syntax or format guidance beyond the schema. Baseline 3 applies.

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?

States a specific verb and resource (view DAC usage report) plus the report's content dimensions: spending by service, period, and transaction type. This distinguishes it from the sibling get_dac_balance (point-in-time balance vs. historical breakdown), though it never names that sibling explicitly.

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?

'Useful for budgeting and trajectory analysis' implies the use case but gives no explicit when-to-use or when-not-to-use guidance and never routes the agent between this and get_dac_balance or the various session/anomaly siblings.

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