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

Annotations already declare readOnlyHint=true, destructiveHint=false and openWorldHint=false, so the safety profile is covered. The description adds real behavioral context beyond that: the default estimator, that a column can be subtracted row-by-row before analysis (delta-Ct), that the design is sized both at the estimate and at the interval limit nearest zero, and what the output feeds into.

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?

Front-loaded with the core purpose ('The effect a power calculation needs...'), and the second sentence cleanly covers the return/handoff. The prose is dense and jargon-heavy with a provenance aside ('effectsize 1.0.3, reproduced'), but each clause carries substantive information rather than filler.

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 values need not be spelled out, and the description still notes what the result is used for. For a 16-parameter statistical tool with full schema coverage, the description gives enough to call it correctly; the main gap is the absence of explicit alternatives/preconditions.

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 description coverage is 100%, so the schema already documents all 16 parameters including the estimator choices, paired/pooled_sd constraints and group/reference defaults. The description echoes the estimator default and the subtract-for-delta-Ct behavior but adds little parameter syntax or format detail beyond the schema, so the baseline 3 is appropriate.

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 (estimate/measure) and resource (effect size from pilot data) and immediately frames it against the alternative ('measured from a pilot instead of guessed'). It also distinguishes itself from the sibling calculate_power by noting it 'Returns the `design` calculate_power takes', so an agent can place it in the workflow without opening either 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?

Clear context: use this when you have pilot measurements and need the effect size a power calculation requires, and it explicitly hands off to calculate_power. It stops short of naming when NOT to use it or listing other alternatives (e.g. calculate_rnaseq_power), so no explicit exclusions.

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