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

Annotations already declare the full safety profile (readOnlyHint, idempotentHint, destructiveHint=false, openWorldHint=false), so the agent knows this is a safe, repeatable, local reference read. The description adds only provenance ('eSIM Go /networks parity endpoint, built-in reference'), which lightly reinforces openWorldHint=false, but offers no rate-limit, auth, or freshness context. With annotations carrying the burden, a 3 is appropriate.

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, front-loaded with the triggering condition, so the agent gets the key selection cue first. The trailing clause about the '/networks parity endpoint' is developer-oriented jargon that contributes little to selection or invocation, slightly diluting the sentence.

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 low-complexity, read-only, one-parameter lookup with a rich annotation set and an output schema, the description covers enough for correct invocation. The remaining gap is boundary-setting against heavily overlapping siblings, which is not addressed.

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 single 'country' parameter is fully documented in the schema (100% coverage, with an example 'Japan'). The description adds no format guidance beyond that, so the schema does the heavy lifting and the baseline of 3 applies.

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 concrete verb+resource ('which mobile networks operate in a country') that maps directly to the name list_country_networks. However, it then broadens the scope to 'eSIM support / Wi-Fi / internet-freedom facts,' which overlaps with siblings like check_internet_freedom, find_free_wifi, and get_country_fact_sheet without explaining how this tool differs from them.

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 an explicit trigger ('Use when the user asks which mobile networks operate in a country'), which is clear context for invocation. It stops short of naming when-not to use it or pointing to the overlapping siblings (check_internet_freedom, find_free_wifi), so an agent must still guess at the boundary.

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