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

Annotations already declare readOnly, idempotent, openWorld, and non-destructive, so safety is covered. The description adds one genuine behavioral caveat beyond that – 'Country and language filters never restrict likes' – which discloses a targeting rule the agent would otherwise not know, but it is terse and does not explain the ordering or scope of the returned 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?

Two short sentences with no filler, and the substantive content (URN output, filter caveat) comes early. The only waste is the opening line, which merely restates the tool title verbatim.

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 a zero-parameter read tool is inherently simple. Still, the dangling 'never restrict likes' clause is not unpacked, and the description never says whether the list is global or scoped to a boost/account, leaving a meaningful gap for an open-world lookup.

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 and the baseline of 4 applies. The schema is empty and the description correctly does not invent argument semantics.

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?

The description names a specific verb and resource ('list Post Boost Countries') and adds a scoping detail: it returns 'Country URNs for comment targeting,' which tells the agent what the payload actually is. It does not distinguish itself from siblings such as listPostBoosts or getPostBoost, so it falls short of a 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: the agent can infer this is the lookup to call when it needs valid country URNs before targeting comments. There is no explicit when-to-use, no prerequisite statement, and no named alternative, so it is minimum viable rather than strong.

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