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

annotations already declare readOnlyHint=true and openWorldHint=false, so the safety profile is covered by structured data. The description adds only that omitting service broadens the result set; it doesn't say whether results are counts versus actual numbers, ordering, or freshness.

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 sentences, no filler, and the core operation is front-loaded before the optional-parameter note. Every clause carries information the agent needs.

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 two-parameter read tool with no output schema, the description covers what the tool returns conceptually (a count of in-stock numbers). It stops short of describing the response shape or whether multiple services yield multiple entries, a minor gap.

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%, so baseline is 3, but the description adds real semantics beyond the schema by explaining the behavior of omitting the optional `service` parameter (returns stock across all services) rather than merely restating it.

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 specific verb ('Get') and resource ('how many numbers are in stock'), scoped by country and optionally service. It is distinguishable from siblings like get_pricing and get_balance by the 'stock' framing, though it doesn't explicitly contrast with 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?

The one guidance offered is 'Omit `service` to list stock for every available service,' which clarifies an optional usage pattern. However, it never says when to prefer this over get_pricing or get_rental_offers/what services are eligible, so the agent must infer routing.

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