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

Annotations already declare readOnlyHint=true, idempotentHint=true, destructiveHint=false, and openWorldHint=false, so the safety profile is covered. The description adds the GCD method and return behavior, but does not disclose any auth needs, rate limits, or side effects beyond what annotations provide. No contradiction is present.

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 short and front-loads the purpose in the first sentence. However, the parameter sentence contains inaccurate information, and the return-value sentence is redundant because an output schema exists, so not every sentence 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 simple two-parameter math calculator with an output schema and rich annotations, the description covers the core purpose and usage context. The fabricated optional 'c' and incorrect parameter names leave a notable gap that could cause an agent to make an invalid call.

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% with 'numerator' and 'denominator' documented. However, the description says 'Inputs: a, b (and optional c),' which mismatches the actual parameter names and invents an optional 'c' that is absent from the schema and blocked by additionalProperties=false. This is misleading rather than additive.

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 a specific verb and resource: 'Simplify a ratio to lowest terms using GCD.' It distinguishes the tool from sibling calculators and points to list_bundles for related math tools, so an agent can identify its purpose immediately.

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 gives explicit usage contexts: 'Use for proportions, mixing, or scaling.' It does not name a direct alternative to use instead, so it stops short of a 5, but the intended use cases are clear.

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