util_stddev

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

No annotations are provided, so the description carries full burden. It correctly identifies the tool as non-destructive and purely computational. It does not disclose edge case behavior (e.g., handling of single-element arrays), but the schema's minItems:1 covers that. Overall, sufficient for a simple math function.

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 sentences with no wasted words. Front-loaded with the core purpose and an optimization hint. 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 math utility with no output schema and straightforward behavior, the description is complete enough. It covers the core function and a key usage optimization. Missing details like result format are not critical for selection.

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 descriptions for both parameters. The description adds value by explaining the optional 'average' parameter's purpose (avoid recalculation), which goes beyond the schema's basic description.

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?

Description clearly states the tool computes population standard deviation (denominator n). The verb 'calculate' and resource 'array' are explicit. The name 'util_stddev' matches the description, and it is clearly distinguishable from sibling utilities like 'util_average' or 'util_max'.

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?

Description mentions optional precomputed average to save repeated calculations, giving a clear performance hint. However, it does not explicitly state when not to use this tool or compare it to alternatives, though the name and purpose make it obvious.

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