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

No annotations provided, so description fully shoulders behavioral disclosure. It does not mention output type (likely Boolean), edge cases, or any special behavior. The presence of an output schema mitigates this somewhat, but the description alone is minimal.

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 extremely concise (5 words) with no wasted text. It is appropriately sized for a simple tool, though a slightly more structured sentence could improve clarity.

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 single-parameter deterministic check tool, the description is largely adequate. It lacks mention of return type or edge cases, but the output schema likely fills that gap, making it mostly 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?

Schema coverage is 100% (parameter 'number' has a description). The description adds no extra meaning beyond what the schema provides, meeting the baseline for full coverage.

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 ('Check') and resource ('a number is a Fibonacci number'), clearly stating the tool's purpose. It distinguishes from sibling 'fibonacci' (likely generates numbers) and other Boolean check tools.

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?

No explicit guidance on when to use this tool vs alternatives like 'fibonacci' or other number checkers. The purpose is implied but lacking directional context.

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