vk_get_username_99fb060909c5

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

With no annotations provided, the description carries the burden of disclosing behavior. It discloses that the endpoint usually requires no request body, path/query params are top-level fields, aliases are accepted, and authentication is not required. This is substantive, though it omits error handling or 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?

The description is slightly longer than strictly necessary but every sentence adds value: endpoint identification, output type, body requirement, parameter conventions, and auth. It is front-loaded with the core purpose 'User Avatar'.

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 GET tool with two parameters and no output schema, the description covers purpose, parameters, authentication, and response format. It lacks explicit error behavior but is otherwise sufficient given the low complexity.

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 already provides 100% coverage of parameter descriptions (size and username). The description adds useful information about parameter placement and camelCase/snake_case aliases, which goes beyond the schema and helps the agent construct valid calls.

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 tool's purpose: 'Returns the user avatar as image' and identifies the exact endpoint 'GET /{username}/avatar'. It distinguishes from sibling user tools by specifying the avatar image resource.

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 clear context that this tool is for retrieving an avatar image and notes that authentication is not required. However, it does not explicitly mention alternatives or when not to use this tool compared to other user-related tools.

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