why

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

The annotations indicate a safe read-only, idempotent operation, but the description adds almost no behavioral detail. It fails to disclose what the tool returns, whether it produces an explanation, proof, or comparison, or what side effects (if any) occur. The line about 'what numguard does' is too abstract to inform an agent about invocation behavior.

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 only one sentence and has no structural waste, but it achieves brevity at the cost of clarity. It is under-specified rather than genuinely concise because the sentence fails to convey actionable meaning.

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?

Despite the simplicity (0 params, read-only annotations), the description is not complete enough for an agent to know what invoking this tool accomplishes. No output schema exists, so the description should at least clarify the return value or purpose, but it does not.

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, so the schema already fully covers parameter semantics. The baseline of 4 applies because there is nothing for the description to add regarding parameters.

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 is cryptic: 'What numguard does that computing the number yourself, or a lesser checker, does not.' It never states a concrete action like 'returns' or 'explains,' nor does it specify what resource or result is involved. It distinguishes numguard from alternatives but does not define what the 'why' tool actually does.

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?

There is no explicit guidance on when to use this tool versus alternatives. The description implies a unique value proposition relative to 'computing the number yourself' or 'a lesser checker,' but it does not name sibling tools, prerequisites, or concrete use cases. An agent has no basis to choose this tool.

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