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

Annotations already declare readOnlyHint=false, destructiveHint=false, and idempotentHint=true. The description reinforces the idempotent behavior, adding clarity that repeated calls won't cause errors, and mentions it accepts two input formats, which is useful beyond the schema. It doesn't contradict annotations.

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?

Three short sentences, front-loading the core purpose, then input format and idempotency. Zero redundancy, every sentence carries useful signal for an agent.

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 tool with 2 parameters and full schema coverage, the description covers the essential behavior: what it does, how to input, and the idempotency guarantee. It could optionally mention what happens if the country is already visited, but the idempotency hint implies it's safe, so completeness is high but not perfect.

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 100%, with both parameters documented. The description adds minimal extra meaning, only reinforcing the country format (ISO-2 or name) which is already in the schema. It doesn't add detail about the notes parameter beyond what schema provides, so baseline 3 is appropriate.

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?

Clearly states the action (mark as visited), the resource (country), and the input format (ISO-2 code or name). Distinguishes from siblings like remove_country and add_place by explicitly focusing on countries and the visited status.

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 description implies usage in a travel-tracking context and mentions idempotency, which guides when to call it repeatedly. However, it doesn't explicitly contrast with siblings like add_region or add_place, though the name and scope are clear enough for most agents.

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