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

Annotations already declare readOnlyHint=true, so the safety profile is covered by structured data. The description adds two useful behavioral facts beyond that — the required country scope and that pickup-point support is reported per courier — but says nothing about result volume, pagination, or error behavior when a country has no couriers.

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 short clauses, front-loaded with the primary purpose, followed by the distinguishing return attribute and the endpoint. No filler and nothing to trim.

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 simple, fully documented read-only list tool with annotations covering safety, the description is nearly sufficient; an agent knows what it returns at a high level. It stops just short of noting pagination defaults or the case where no couriers exist for a country.

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%, with page, limit, and country_code all documented in the schema, so the baseline is 3. The description reinforces country_code as the scoping input but adds no format or interaction detail beyond what the schema already says.

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 ('List the couriers') plus its scoping dimension ('available for a country') and the key attribute returned ('whether each one handles pickup points'). That is far more than a restatement of the name, though no sibling tool overlaps so no differentiation is needed — hence 4 rather than 5.

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 only implied: an agent can infer this is the lookup to call when it needs courier options for a destination country. There is no explicit when-to-use, no stated prerequisites, and no mention of what to do instead if the country is unsupported.

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