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

Annotations already declare readOnlyHint=true and openWorldHint=false, so safety and the closed/fixed nature of the data are covered. The description adds the useful detail that returned names are the exact ones accepted by the contact endpoints, but says nothing about ordering, caching, or size of the list.

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, zero filler, with the resource and its intended use front-loaded. Nothing could be removed without losing information.

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?

An output schema exists, so return values need no explanation, and the zero-parameter schema needs none either. The description covers purpose and usage; only minor details such as list size or stability are missing, which is acceptable here.

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 nothing for the description to disambiguate; baseline 4 applies. Mentioning that the IDs pair with country names implicitly tells the agent what the output values are for.

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 (List) plus specific resource (ConnectReseller country names and IDs), with the qualifier 'exact' signaling that these are the provider's canonical values, not arbitrary ISO codes. It is clearly distinguishable from the sibling list_contact_states, though that distinction comes from the tool name rather than the description.

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?

'for creating or updating contacts' gives a clear use context that links the tool to create_contact and the contact-update siblings. It does not state exclusions or name an alternative lookup source, but for a zero-parameter reference lookup the when-to-use signal is adequate.

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