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

Goes well beyond the annotations (readOnly/idempotent) by disclosing an auth prerequisite (API key on a paid Tides plan), the default window behavior, the plan-dependent cap on days, and a subtle behavioral trait — elevation shifts sun/moon times by roughly three minutes but never tide heights.

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-loads what the call returns, then usage, then the elevation nuance, defaults, and key requirement — each sentence carries distinct information. Dense but no filler; slightly long for the payload.

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 no output schema, the description enumerates the returned per-day data, and it covers defaults, plan limits, and auth. Nothing an agent needs to invoke it correctly 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 already 100%, so baseline is 3, but the description adds real meaning: it quantifies elevation's effect (~3 min) and clarifies that tide heights are observer-independent, which disambiguates the parameter's scope. It does not add syntax beyond the schema for tz/days/start_date.

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+resource: per-day high/low waters plus sunrise, sunset, golden/blue hour, twilight and moon phase. It explicitly distinguishes itself from the sibling tools get_tide_extremes and get_sun_moon_times, so an agent can select it without opening the 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?

Names the two alternatives it replaces (get_tide_extremes, get_sun_moon_times) and the reason to prefer it (single call). It also gives conditional guidance on when to pass elevation ('when you know it') and when to omit it.

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