get_supported_countries

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

No annotations are provided, so the description carries the behavioral burden alone. It discloses that the tool is a read-only enumeration returning JSON, but says nothing about whether the country list is static or filtered, caching, or the response shape. For a zero-parameter lookup the risk is low, but the disclosure is thin.

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 short sentences with zero waste, and the core purpose is front-loaded ahead of the usage hint.

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 no-argument reference tool with no output schema, the description covers what it returns and why an agent would call it. The only minor gap is the exact structure of the returned country list, which 'Returns JSON' leaves unspecified.

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 has zero parameters and 100% coverage, so there is nothing for the description to compensate for. Baseline of 4 applies for a parameterless tool.

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+resource ('Returns list of supported countries') and scopes it to market data and screeners, which distinguishes it from the stock/financial siblings. It does not name a sibling directly, so it falls short of a 5, but the purpose is unambiguous.

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?

'Use to find valid country codes for other tools' gives explicit when-to-use guidance and ties it to a downstream workflow. There is no when-not guidance or named alternative, but for a reference lookup tool the trigger condition is clear.

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