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

Annotations already declare readOnlyHint=true, destructiveHint=false, and openWorldHint=false, so the safety profile is covered. The description usefully clarifies that 'revenue' means completed payments rather than booked/invoiced amounts, but says nothing about currency, timezone, or response shape.

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 sentences, both load-bearing: the first defines metric and scope, the second gives the follow-on rendering call. Nothing is duplicated from structured fields and nothing is wasted.

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, no-output-schema aggregation tool, the definition of the metric plus the chart guidance is nearly sufficient. Minor gaps remain around units/currency and whether the series is zero-filled for empty months.

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, so there is nothing for the description to disambiguate and the baseline is 4. The absence of an adjustable date range is implied by the fixed 'last 12 months' wording, which the agent can rely on.

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 metric (collected revenue), narrows it with a precise definition ('completed payments'), scopes it by time ('by month, last 12 months'), and names the intended rendering tool. An agent can distinguish it from siblings like activity_summary or ar_aging without opening a schema.

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?

Gives a concrete usage pattern — pipe the result into render_chart with xField='month' and yField='revenue' — which tells the agent what to do next. It does not say when to prefer this over neighboring revenue/summary tools or list exclusions, so it stops short of a 5.

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