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

Annotations already declare this a safe, idempotent, non-open-world read, so the safety profile is covered. The description adds genuine value beyond that by enumerating the returned elements and by disclosing the empty:true sentinel and how to handle it — a non-obvious behavioral contract that prevents the agent from misreporting missing data as an error.

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, no filler, with the core purpose front-loaded and the edge-case handling second. Every clause carries information an agent needs.

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 and zero required parameters, the description does the necessary work of naming the return fields and the empty-result path. It could go slightly further on how the month parameter affects the percentile window, but nothing essential is missing for a correct call.

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% for both parameters, so the schema already carries the syntax. The description adds only the default behavior for compare_country (falls back to the saved compare-country) and says nothing about how month interacts with the result or what happens on an invalid country code, so baseline 3 is appropriate.

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 (returns the user's net-worth percentile) plus the two scoping dimensions that define it: age band and country. This cleanly separates it from the raw-value sibling get_net_worth without needing to name it.

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 explicit guidance for the empty-result branch (relay message and next_step_url rather than treat as an error), which is real usage direction. However it never says when to prefer this over get_net_worth or project_retirement, so the tool-selection decision is left implied.

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