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

Beyond the annotations (readOnlyHint, idempotentHint, destructiveHint), the description discloses meaningful behavioral details: live rates, how billing works, whether free welcome credit covers the first call, and that the response includes a dialer link set to the country. It also flags that premium, satellite-adjacent, and special-service numbers are quoted at their own higher rate. This substantially exceeds what annotations convey and contains no contradictions.

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 core purpose is front-loaded in a clear first phrase, followed by a list of value-added outputs and a single second sentence for an edge case. It is somewhat list-heavy but every clause contributes, and there is no redundant filler or restatement of the tool name.

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 read-only, zero-required-parameter price tool with an output schema, the description is complete. It explains what result content will be returned, the country-versus-number input distinction, premium prefix behavior, and the dialer link. An agent has all the context needed to invoke it correctly without additional clarification.

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%, so both 'number' and 'destination' are already fully documented in the input schema. The description adds a useful behavioral nuance (dearer prefixes get their own rate) but does not introduce new parameter semantics or format guidance beyond the schema. The baseline 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?

The description states a clear verb and resource: it retrieves the per-minute price of calling a country or a specific number from a web browser. It enumerates additional outputs (live rates, free-credit check, billing, dialer link) and the title adds scope. However, it does not explicitly distinguish itself from the sibling get_dialing_instructions, so it earns a 4 rather than 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?

The description implies this tool is for price lookups, but it never says when to use it versus get_dialing_instructions or provides any exclusion criteria. There is no explicit when-to-use or when-not-to-use guidance, leaving the agent to infer the tool's niche from its name and purpose.

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