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

Annotations already declare readOnlyHint=true and openWorldHint=false, so safety is covered. The description adds the crucial non-persistence behavior ('WITHOUT saving it'), which annotations do not convey, and clarifies ad-hoc spec computation. It doesn't discuss rate limits or result format, but for a read-only compute tool that's acceptable.

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?

Three sentences, front-loaded with what it computes, then usage examples, then the alternative. No waste. Slightly verbose in examples but each earns its place by grounding the abstract 'analytics insight' phrase.

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?

Given a single required 'spec' parameter with 100% schema coverage, read-only annotations, and no output schema, the description covers purpose, usage, and the non-persistence behavior. The remaining minor gap is not naming the output shape for the agent, but the schema's vizType description handles that.

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 coverage is 100% and the embedded schema description already enumerates vizType values and gives period guidance (relative.value='this_month'). The description names the same output categories but doesn't add spec-syntax or default details beyond what the schema provides. Baseline 3 is correct when 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?

States a specific verb (Compute) and resource (analytics insight) and enumerates the four output shapes (single value, comparison, breakdown, time-series). It explicitly contrasts with propose_saved_insight, making sibling differentiation 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?

Gives a clear when-to-use condition (one-off analytical questions) with concrete examples, plus an explicit when-to-use-the-other-tool condition (keep result pinned on dashboard → propose_saved_insight). This is textbook alternative routing.

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