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

Annotations already declare readOnlyHint=true and openWorldHint=false, so safety is covered. The description adds genuine operational context beyond that: the full dosing formulas and the chemical-addition limits (max ~50 ppm raise at a time, max 1 quart acid per 10,000 gal), which constrain how results should be acted on.

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?

Purpose and the empty-state intent are front-loaded, then the formula and per-chemical coefficients are packed into a few dense clauses with no filler. Slightly formula-heavy for a description, but every sentence carries information.

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?

No output schema exists, and the description compensates by naming output units for each case (lb, fl oz) so the agent knows what the result represents. With only 3 numeric inputs and full schema coverage, the definition is sufficient; it stops short of describing the response object's shape but nothing critical is missing.

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 schema already documents each field's meaning and defaults. The description goes further by showing how each input is used in the formula (|target − current|, gallons ÷ 10,000), clarifying the relationship between parameters rather than restating them.

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 ('how much baking soda raises ... total alkalinity, or muriatic acid ... lowers it') and names the dosing basis (published doses per 10,000 gallons). An agent can distinguish it from the many sibling calc_pool_* tools (chlorine, salt, calcium, stabilizer) at a glance.

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?

Gives clear context: it branches on direction (raise vs lower) and names the specific chemicals and units for each case, which implicitly tells the agent when each path applies. However, it never names a sibling or states when NOT to use it (e.g., that it does not compute pH or volume).

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