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

Annotations already declare readOnly/idempotent/non-destructive, and the description adds scope facts the annotations cannot express: a fixed catalog of 37 countries and the fact that a filtered call returns a richer payload (full input schema) than an unfiltered one. It omits what happens with an unrecognized country code, which is the one behavioral gap.

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 unfiltered return contents front-loaded and the filtered behavior second. Every clause earns its place by describing a distinct part of the response contract.

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 does the necessary work of enumerating return fields and the calculation-type vocabulary. It is nearly complete for a one-optional-param list tool, missing only the behavior for invalid country codes.

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 already 100% with examples, so the schema carries the basics. The description adds meaning beyond it: the parameter is optional (whole catalog when omitted) and, critically, changes the response shape by including the full input schema for that country.

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 and enumerates exactly what is returned: country code, currency, calculation type, calculator page, methodology, and sources. Naming the calculation families (uk-drawdown, au-super, income-gap) directly ties it to the sibling calculate_* tools, so an agent can tell it apart without opening a schema.

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?

"With a country code, returns that country only, with its full input schema" clearly signals the discovery/browse use case that precedes the calculate_* calls, and the no-argument case is implied as the full-list browse. It does not explicitly say when not to use it or state prerequisites, so it stops short of a 5.

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