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

With no annotations, the description carries the full behavioral burden and does add real value: it declares the data source as JMA astronomical tide estimation rather than a forecast, and bounds the date range to 2026-01-01 through 2027-12-31. It omits failure behavior (out-of-range dates, unknown stations) and the shape of the returned tide table, leaving notable gaps for an unannotated tool.

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?

The returned data is front-loaded in the first clause, with the range limit, the days option, the hourly option, and the data-source caveat each in compact trailing fragments. Dense but every fragment carries information; no 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?

No output schema exists, so the description must describe return values, and it does enumerate the fields returned (tide times, levels in cm from the datum, moon age, tide type, moon phase). Given a simple 4-parameter read tool, this is nearly complete, with only error/edge-case behavior and the unit/shape of hourly output left unstated.

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 all four parameters are already documented, and the description mostly restates them (days up to 7, include_hourly for hourly levels). The only marginal addition is the framing of the station-name-vs-code ambiguity, which the schema already describes. Baseline 3 applies when the schema does the heavy lifting.

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 the specific resource set it returns (high/low tide times and levels, moon age, tide type, moon phase) for a given station and date, with an explicit valid date range. It distinguishes itself from weather siblings by stating it is JMA astronomical tide calculation, not a forecast, but it never names the closest siblings (next_tide, list_tide_stations) to sharpen the boundary.

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?

It gives implied usage cues (days for up to 7 consecutive days, include_hourly for hourly levels) and notes that ambiguous station names return candidates, which guides the call pattern. However, it never states when to prefer it over next_tide or how to first resolve a station via list_tide_stations, so the agent must infer the alternative routing.

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