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

Annotations already declare readOnlyHint, idempotentHint, openWorldHint=false, and destructiveHint=false, so the safety and determinism profile is fully covered. The description adds one useful constraint not in annotations (standard deviation must be positive), but nothing about numeric precision or edge cases. With annotations covering behavior, a 3 is appropriate.

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?

A single, front-loaded sentence that wastes no words. Every clause (verb, resource, required inputs, positivity constraint) 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?

An output schema exists, so return-value explanation is unnecessary, and annotations cover the safety profile. The description covers inputs and the positivity constraint, but for a numeric tool it could note edge cases (e.g., division-by-zero guard already enforced by schema, or rounding behavior). Such minor gaps keep it below a 5, but it is adequate.

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%, so the baseline is 3. The description adds meaningful semantics beyond the schema: it specifies that standardDeviation must be positive, which is real guidance beyond the schema's generic 'Standard deviation.' label, and the example value of 10 illustrates the intended scale.

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?

States a specific verb (compute) and resource (standardized z score) and enumerates the exact inputs needed (value, mean, positive standard deviation). This is distinct from siblings like average_calculator or percentage_calculator, so an agent can tell it apart without opening the schema.

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 implies usage by naming the inputs, but provides no explicit when-to-use guidance or alternatives. With ~90 sibling calculators, some routing context (e.g., 'use for standard-score normalization, not percentages') would be valuable but is absent.

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