Get customer count for a country

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

With no annotations provided, the description carries the full burden and discloses key behaviors: case-insensitive matching and that unknown countries return 0 rather than an error. This is valuable, though it omits details like return format or potential rate limits.

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 with zero waste. The main purpose is front-loaded, followed by two crucial behavioral notes and a usage example. Every sentence earns its place.

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 single-parameter tool, this is complete: it explains what it returns, how the parameter behaves, and the edge case for unknown countries. The lack of an output schema is acceptable since the return type ('count') is implied, and no nested objects or enums exist.

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 input schema provides only a bare string parameter with no description (0% coverage). The description adds meaning by explaining case-insensitivity and the handling of unknown countries, which goes beyond what the schema offers.

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 the verb 'Returns' and the resource 'how many customers are registered in a given country', making the tool's purpose unambiguous. It is distinguishable from siblings like 'get_top_countries_by_customers' by focusing on a single country count rather than ranking.

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?

Provides explicit usage context with the example 'how many customers are from Germany?' and clarifies the unknown-country behavior. However, it does not mention when to use alternatives (e.g., ranking tools) or when not to use this tool, though the clear example partially compensates.

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