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

With no annotations, the description carries the burden of behavioral disclosure. It does disclose the success/error status codes, which is useful, but it fails to explain how the API key is supplied (since the schema has zero params) or mention any potential side effects. The 200/403 detail is valuable but the input mechanism remains opaque.

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 one efficient sentence that conveys the core purpose and expected responses with zero waste. It is ideally concise and front-loaded.

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 tool with no schema, annotations, or output schema, the description covers the essential purpose and responses. The only gap is the lack of explanation on how the API key is provided, but given the zero-parameter design, this is likely handled externally, making the description largely complete.

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?

There are zero parameters, so the baseline is 4. The description identifies the subject (API key) but does not clarify how the key is transmitted, given the empty schema. However, since no parameters are expected, the description does not need to detail parameter values; still, a note about implicit authentication context would improve it.

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 uses a specific verb 'validates' and the resource 'API key', clearly stating what the tool does. It also provides distinct status codes (200/403) that set it apart from sibling tools, which are all media-related.

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 implicitly indicates this is for checking API key validity, but it does not explicitly state when to use it or mention any alternatives. Given that all sibling tools are unrelated, some contextual guidance on when to invoke validation would be helpful.

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