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

Annotations already declare readOnlyHint and openWorldHint, so the safety profile is covered. The description adds a genuine behavioral constraint not carried by the annotations (or fully by the schema): results past 30 days require a pass key, which ties this tool to the coast_map_pass/pass_status siblings. It still says nothing about response shape, pagination, or whether results are empty outside coverage.

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?

A single dense sentence with the resource and lookahead window front-loaded and no filler. It could be tightened slightly ('over the next days' is a little vague about the window boundary).

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 only hints at the return ('marking the good ones') without saying how tides are scored or ranked. It also never addresses the location requirement (station code vs lat/lng) even though zero parameters are required, leaving the agent to work that out from the schema alone.

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 75%; lat, lng, and station are documented in the schema itself. The only real addition is for the undescribed 'days' parameter, and even that largely restates the schema's default=30 and maximum=90, with the pass-key caveat being the sole new information.

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 names a specific resource and scope: the lowest daylight low tides over a lookahead window, with an explicit use case (clamming, foraging, tide pools). It is clearly distinguished from marine_forecast or currents by being about low tides, but it never names the closest sibling, tide_times, so an agent must infer the split itself.

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?

Usage is implied through the activity framing ('for clamming, foraging and tide pools') and the lookahead default, but there is no explicit statement of when to choose this over tide_times, marine_forecast, or plan_paddle, and no exclusions.

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