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

Annotations declare readOnlyHint=true and destructiveHint=false, so the safety profile is already known. The description adds valuable behavioral details: the exact endpoint, the alias nature of X-API-Key, and explicitly states it does not echo the secret, which is a critical security behavior. This goes beyond the annotations to inform the agent about side-effect-free operation and data handling.

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 concise sentences, no filler. The most critical usage information (endpoint and credential formats) is front-loaded, and the security note is a valuable addition. Every word 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 zero-parameter tool with a trivial operation (key verification), the description is nearly complete. It covers input method, endpoint, security behavior, and alias clarification. Missing are details on the response format or success criteria, but the absence of an output schema and the simplicity of the task make this acceptable.

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 tool has zero parameters, and schema coverage is 100% (empty schema). The description compensates by clarifying how the key is passed (via header or env var), which is not in the schema. This effectively explains the implicit input mechanism, which is essential for the agent to use the tool correctly.

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: verifying a caller's API key via a specific endpoint ('GET /keys/verify'). It explicitly mentions the accepted credential formats (SHELF_SMOKE_API_KEY or Authorization: Bearer), which is specific and distinguishes functionality. The mention that 'X-API-Key' is only an alias adds precision.

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 the endpoint and credential formats, implying correct usage. However, it lacks explicit guidance on when to use this tool versus alternatives; among siblings, 'smoke' might be a related check, but no comparison is made. No prerequisites or context for when this verification is appropriate is given.

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