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

Annotations already declare readOnly, idempotent and non-destructive, so the safety bar is met. The description adds real value beyond them: the methodology (published publisher bitrates, median page weight), the caveat that GPS/mail/cloud/tethering values come from the user with no official figures, and that the result is indicative.

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?

Front-loaded with the core purpose, followed by usage, then caveats and source. Dense but every clause (bitrate sources, optionality, caveat, indicative disclaimer) earns its place.

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?

An output schema exists, so return values need not be explained. The description covers methodology, optionality, data limitations and provenance, which is largely complete for a 14-param estimation tool, with only per-parameter detail left to the schema.

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?

At 50% schema coverage across 14 params, description carries moderate burden. It usefully states all parameters are optional and clarifies which inputs are user-supplied rather than official, but many numeric parameters (hours per week, workdays, web pages) remain unexplained beyond the schema.

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: estimating a user's monthly data consumption in GB with a breakdown by usage and sources. It is clearly distinct from pricing/eligibility siblings, though it does not name any sibling explicitly (e.g. recommend_plan or compare_plans).

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 gives explicit when-to-use context: 'chiffrer un besoin avant de choisir un forfait', which ties it naturally to plan-selection siblings. It does not, however, state when-not to use it or name an explicit alternative.

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