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

Annotations already declare readOnly/idempotent/no-destructive, so the safety profile is covered. The description adds genuine domain behavior beyond that: 20 markets collapse to 14 rule sets, the seven EU markets share one food-law set with national riders, and UK is a label while machine fields carry ISO GB. The only gap is what happens for an unmapped input.

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-loads the intent question, then compresses scope, rule-set counts and the UK/GB edge case into one tight block. The parenthetical is information-dense but slightly crammed; no sentence is wasted.

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, return values need not be explained, and the description covers input formats, scope and the label/ISO distinction. Only the failure behavior for unknown destinations is unaddressed, which is a minor gap for a single-param read tool.

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 0%, so the description must carry the single parameter. It does so well with six examples ('DE', 'US-CA', 'UK', 'FR', 'EU-NL', 'JP') that reveal accepted formats (bare country, subdivision, region-prefixed) and the UK-vs-GB mapping quirk. It still doesn't specify how invalid or ambiguous values are handled.

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?

Specific verb ('Resolve') plus precise resource ('a ship-to ... to one of the 20 markets and its rule set'), with concrete input examples. An agent can immediately distinguish this from siblings like get_market_status or resolve_actor without opening any 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?

The opening 'Where is this going?' implies the intent (routing a destination to its rule set) and the examples show valid inputs, but there is no explicit when-to-use/when-not-to-use guidance and no sibling is named as an alternative. Usage is implied rather than stated.

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