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

With no annotations and no output schema, the description carries the full burden, and it delivers real value by describing the returned rows: provider alias, operator, price, stock count and deliverability — exactly what an agent needs to chain into order_number. It omits auth requirements, rate limits and pagination behavior, which keeps it short of a 5.

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 sentences, no filler, and the core operation is front-loaded ahead of the constraint and the response-shape note. Every sentence contributes a distinct fact.

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 two-parameter read tool with no output schema, the description covers the key constraint and the shape of returned rows, which is enough to invoke and consume it correctly. Auth and error/timeout behavior remain unstated, leaving 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 description coverage is 100% and both parameters are documented (country code/name/slug, service slug), so the baseline is 3. The description's mutual-dependency rule ('at least one of country or service') is genuinely beyond the schema, which marks both as optional, but it doesn't clarify formats or disambiguation beyond that.

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 and resource ('Get real-time pricing for a country and/or service') and names the scope dimensions. However, it does not differentiate itself from close siblings like get_number_pricing or quote_esim, which an agent could easily confuse with this tool.

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?

It supplies one concrete usage constraint ('At least one of country or service must be provided') and points to order_number as the downstream consumer of the returned operator rows. But it never says when to prefer this over get_number_pricing, quote_esim, or get_number_renewal_options, so alternative selection is left to inference.

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