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

readOnlyHint=true already tells the agent this is a safe read, so the description only needs to add scoping context — which it does by making clear the figures are limited to "this agent key." It does not mention rate limits, default period behavior, or data freshness, so it adds some but not rich behavioral context beyond the annotation.

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, front-loaded with the scope and metric list before the usage cue, with essentially no filler. Slightly denser metric enumeration would be the only improvement.

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?

With no output schema, the description usefully enumerates the metrics returned, so an agent knows what to expect. Combined with the readOnly annotation and fully documented parameters, the only gap is the absence of any return-shape or aggregation granularity detail.

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%, including the 1-90 day bounds and the explicit 'never make one up' warning about agent_key, so the schema carries parameter meaning. The description only references 'a period' without adding format or default details, which is the expected baseline when the schema does the heavy lifting.

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 gives a specific verb and resource ("Show this agent key's statistics for a period") and enumerates the metrics returned: tool calls, offers shown, clicks, conversions and earnings. It is clearly distinguishable from siblings like get_offer or claim_earnings, though it does not name those siblings 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?

It states a concrete trigger: "Use when your developer or the key owner asks how the integration performs." That gives an agent a clear condition for selecting this tool. It stops short of stating when not to use it or pointing at alternatives, so it falls below the top band.

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