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

With no annotations, the description fully discloses behavioral traits: determinism, fixture verification, guest rate limits, API key usage for member budget, and the return of a Guild-signed provenance envelope. It also states the 10k number limit, covering important operational characteristics beyond what the schema alone conveys.

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 compact but information-dense, covering output statistics, input constraints, authentication, and provenance in a few sentences. It is front-loaded with the core purpose and avoids redundancy, though the embedded JSON Schema adds length. Every sentence contributes value, deserving a 4.

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?

Given the tool's complexity and the presence of an output schema, the description is highly complete. It explains what the tool computes, the input shape, the output envelope, rate limits, authentication, and determinism guarantee. No critical context is missing for an agent to decide whether and how to invoke it correctly.

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?

Though schema description coverage is 0%, the description embeds the complete payload JSON Schema, explicitly defining 'values' (array of numbers, min/max items) and 'percentiles' (array of numbers 0-100). It also explains the api_key parameter's purpose (guest rate limit vs member budget), providing far more meaning than the generic input schema.

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 the tool computes deterministic descriptive statistics for a numeric series, listing specific statistics (count, sum, min, max, mean, median, stdev, variance, percentiles). It distinguishes itself from siblings by emphasizing exact arithmetic rather than model estimation, which is unique among the listed 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?

The description provides clear context for when to use the tool: when exact, deterministic statistics are needed for up to 10k numeric values. It implies it should be used over model-based estimation ('Exact arithmetic instead of model estimation'), but does not explicitly name alternative tools or state when not to use it, keeping it just below a 5.

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