List Rental Country Availability

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

Annotations already declare readOnlyHint=true, idempotentHint=true, and destructiveHint=false, so the description does not need to repeat those. It adds valuable context about what data is provided (available counts, pricing, per-country service counts) and how tier affects the data source (local vs. global supplier network). This goes beyond the annotations, though it could mention that the response is a list or that it may be empty, but the current level is sufficient.

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?

The description is two sentences, with the core purpose and key behavior front-loaded. It is efficient, but the second sentence could be seen as slightly dense with details (e.g., 'with per-country service counts and popular services'), though it's still concise. No waste, but the sentence structure is a bit packed. Still, it earns a 4.

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?

Given the tool's moderate complexity, the description covers the main entry point (tier) and usage context ('before creating a rental'). The annotations cover safety and idempotency, and the schema covers parameters. There is no output schema, but the description explains what the tool returns (list of countries with stock, counts, pricing) so expectations are set. Some might argue it could mention that the output is a list, but it's clear enough. It's complete for an internal directory-like tool.

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 schema description coverage is 100%, so the schema already documents all parameters. The description adds meaning for the 'tier' parameter by explaining the difference between full_access and platform, which is not fully captured in the schema's terse 'Which tier to list'. For other parameters like 'type', 'country', and 'service', the description does not add further detail, but the schema covers them. Baseline 3 is appropriate since the schema carries the load.

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 clearly states 'List countries with rental stock, available counts, and pricing,' which is a specific verb and resource. It also differentiates between the two tiers with distinct inventory sources, making it distinguishable from siblings like virtualsms_list_countries or virtualsms_rentals_pricing. The title is descriptive, and the description adds crucial details about what each tier returns.

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 provides clear guidance on when to use this tool ('Use this before creating a rental') and explains the meaning of the tier parameter choices ('full_access (default) shows local-SIM inventory; tier=platform shows countries available via our global supplier network'). It does not explicitly state when NOT to use it versus alternatives, but the context of 'before creating a rental' is helpful, and the sibling resolution is aided by the distinct purpose.

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