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

The annotations already declare readOnlyHint=true, idempotentHint=true, and closed-world scope, so the safety profile is covered. The description usefully adds that the tool both computes an estimate and suggests a plan size, but says nothing about estimation model, rounding, or plan catalog assumptions.

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 trigger condition, then the computation and output. Nothing is redundant and it is appropriately sized for a three-parameter estimator.

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 an output schema present, the description needn't explain return values, and it still names the plan-size suggestion. It covers inputs and trigger adequately; the only gap is the unaddressed relationship to calculate_data_budget and recommend_plan.

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% and all three parameters are required with an enum on usage_profile, so the schema does the heavy lifting. The description merely restates the parameters (trip days, daily hours online, light/moderate/heavy) without adding format, range, or edge-case semantics.

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 and resource ("estimates" data usage) plus its three inputs and the plan-size recommendation it emits. However, it never distinguishes itself from the similarly-purposed sibling calculate_data_budget, so an agent cannot resolve the overlap from the description alone.

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?

"Use when the user is planning a trip and asks how much mobile data they need" gives a clear triggering condition and even the user's phrasing. It lacks any exclusion or pointer to the look-alike sibling calculate_data_budget, so the when-not guidance is absent.

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