list_servers

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

With no annotations provided, the description carries full burden. It discloses the return format (dict with 'servers' key, each server dictionary structure) and implies a read-only operation. It does not mention side effects, authentication, or rate limits, but for a list operation, this is largely sufficient.

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 description uses a clear docstring style with Args and Returns sections, is concise (no redundant information), and every sentence adds value. It is front-loaded with the main purpose.

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 list tool with 3 parameters, an output schema exists, and the description includes return format. It covers filters, constraints, and output structure without missing essential details like pagination or rate limits (which are likely not needed for this simple list).

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 0%, so the description must compensate. It explains all three parameters (country, city, owned_only) with examples and adds a critical constraint (city requires country), providing semantics the schema lacks.

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 explicitly states 'List available Mullvad VPN servers with optional filters,' clearly identifying the verb (list), resource (servers), and context (Mullvad VPN). It distinguishes from siblings like list_cities and list_countries by focusing on servers with detailed fields.

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 provides parameter constraints (city requires country) but lacks explicit guidance on when to use this tool vs. alternatives such as connect, get_status, or list_cities. No when-not-to-use or comparative advice is given.

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