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 bar is lower. The description does add non-obvious context beyond the annotation: every action requires authentication. It says nothing about pagination limits, result volume, or freshness of the analytics, so it adds only modest behavioral value.

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 short lines, purpose first, then the action list, then the auth caveat — no filler. The action list partially duplicates the schema's action field documentation and is wrapped in a leading whitespace artifact, keeping it just short of ideal.

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 compensates by sketching what each action returns (plan limits, per-product breakdown, request timeline), which is exactly what an agent needs to choose among them. It could still say more about the shape of the history timeline or freshness of the data, but nothing critical for invocation is missing.

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%, so the schema already documents action, from, to and limit with formats and defaults. The description's only parameter-level contribution is noting that date filters apply to the history action, which is marginal. Baseline 3 applies 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 states a specific verb and resource ('View API usage analytics for the authenticated user') and enumerates the three supported actions. It is clear what the tool does, but it never distinguishes itself from closely related siblings like agent-billing or agent-subscriptions, which also surface quota/plan information.

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?

Each action is briefly characterized (summary = overview with plan limits, products = per-product breakdown, history = generation request timeline with optional date filters), which gives the agent enough context to pick the right action. There is no explicit when-not guidance or routing to alternative siblings for billing/cost questions.

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