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

With no annotations, the description carries the full disclosure burden, and it does state what the result contains: an enumeration of covered countries and a per-country signal about refusal of animal calls. It omits ordering, completeness guarantees, and whether the refusal flag is always present, so the disclosure is good but not exhaustive for a read-only listing tool.

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?

One sentence defining the payload followed by one sentence of routing guidance — front-loaded and free of filler. The second clause about refusing animal calls is slightly dense but still earns its place by defining a returned field.

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 zero-parameter, non-destructive listing tool with no output schema, the description covers purpose, returned content, and call sequencing. The only gap is any statement about result size or whether all countries are always returned.

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?

The tool takes zero parameters, so there is no parameter meaning to convey; baseline for a no-param schema applies. The description adds no misleading hints about inputs, which is correct.

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 countries") and narrows the scope precisely: countries with a recorded veterinary poison service, plus which of those have a centre that refuses animal calls. The two-facet output makes it immediately distinguishable from find_pet_poison_service.

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 sequencing guidance ("Use this to check coverage before calling find_pet_poison_service") and names the sibling it precedes. It does not say when this call is unnecessary or what to do if coverage is absent, so it stops short of full when/when-not coverage.

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