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

The annotations already declare readOnlyHint=true and openWorldHint=false, so safety is covered. The description adds one genuine behavioral trait beyond them — that results are ranked by all-in cost — but says nothing about data freshness, which fees/spread components make up 'all-in', or what happens with an unrecognized country slug. Adequate, not rich.

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?

A single dense sentence with the action and scope front-loaded and the enumerations relegated to a parenthetical. It is efficient, though the one-sentence packing of three parameter descriptions makes it slightly harder to scan than a short lead line plus a constraints line.

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?

For a read-only calculation tool with three optional parameters and no output schema, the description covers inputs well and hints at output ordering. It leaves the agent guessing about the shape of the result (per-exchange rows? sorted list?) and where the cost data comes from, which matters for a tool whose entire value is a comparative ranking.

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?

With 0% schema description coverage, the description carries the burden and largely does: it enumerates all four mode values, states the amount window ($10 to $1,000,000), and clarifies that country takes a 'slug', which the schema only hints at via maxLength. It omits the defaults (spot_taker, 1000), so it is not complete.

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 opens with a specific verb ('Calculate and rank') and a precise resource ('true all-in USD cost across crypto exchanges'), then scopes it by amount, mode and country. Nothing else in the sibling set (get_country, get_guide, list_providers, search_guides, report_outdated_info) does comparison costing, so an agent can select it without opening the 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?

Usage is implied by the input scoping ('for a given trade amount... order mode... optional country slug'), which tells the agent the situation this tool fits. However, there is no explicit when-to-use or when-not-to-use statement, and no pointer to a sibling for related needs such as listing the exchanges being compared.

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