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

Annotations already declare readOnlyHint=true, idempotentHint=true and openWorldHint=false, so safety and reproducibility are covered. The description usefully enumerates the four returned error variants (percent, absolute, relative, signed) in the absence of an output schema, but says nothing about edge cases such as actual=0 or sign conventions, which matter for an error calculator.

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 compact sentences; the concrete example is front-loaded and immediately conveys the tool's behavior. The trailing URL is promotional rather than task-relevant, a minor deduction.

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?

With two fully documented and defaulted numeric params and no output schema, the description carries the main remaining burden by enumerating the approved return values and giving an example. It would be fully complete if it noted the default inputs or how zero/degenerate denominators are handled.

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, and the worked example ('Measured 9.6 when the accepted value is 9.81') usefully disambiguates the otherwise confusingly named actual vs measured parameters - actual is the theoretical/accepted value, measured is the experimental one. It stops short of noting defaults (9.81/9.6) or the numeric bounds.

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 and resource: 'Get percent, absolute, relative and signed error', which is concretely different from the sibling percentage_calculator and percentage_change_calculator. It never names or contrasts those siblings, so an agent must infer the distinction from the name alone, which keeps it short of a 5.

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?

'For lab reports and experiments' gives a usage context but no when-to-use rule, no exclusions, and no pointer to the closest alternative (percentage_calculator, percentage_change_calculator) for non-error percentage math. Usage is implied from the framing rather than stated.

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