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

Annotations already declare readOnlyHint=true and openWorldHint=false, so the safe-read profile is covered. The description adds genuine value by defining the metric as collected/completed payments rather than billed or invoiced revenue, but reveals nothing about volume, ordering, or edge behaviour (e.g., months with zero revenue).

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 tightly written sentences, no filler, with the metric definition and window front-loaded before the charting hint. Every clause earns its place.

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 zero-parameter read-only aggregate with no output schema, the definition is nearly complete: metric, denominator definition, granularity and range are all stated. The one gap is the return shape (array of month/revenue rows), which the charting hint only partially implies.

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?

The tool takes zero parameters and the schema is empty, so the baseline of 4 applies. There is nothing for the description to clarify beyond confirming that no input is required.

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?

Names a specific metric (collected revenue), an explicit qualification (completed payments), a granularity (by month) and a window (last 12 months) — an agent knows exactly what this returns. It does not name a sibling it differs from, so it falls short of 5, but the resource is unambiguous.

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 second sentence gives downstream usage guidance by mapping the result to render_chart with xField='month'/yField='revenue', which is helpful. However, it says nothing about when to choose this over related aggregates (activity_summary, ar_aging, workspace_usage), so usage is only implied.

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