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

Annotations only cover readOnlyHint and openWorldHint; the description adds genuinely useful behavior not in the annotations — results are in the station's local time, include heights, and are gated at 7 days free vs 90 days with a Coast Map Pass key. It stops short of describing the return format or behavior when the key is missing/invalid.

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 tight sentences: the first front-loads what is returned, the second covers the access limits. Nothing is redundant and no filler is present.

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?

For a 5-parameter, no-required-args tool with no output schema and minimal annotations, the description covers output content (high/low times with heights), time basis, and access limits. The main gap is silence on return structure and on how lat/lng vs station is resolved when both or neither are supplied.

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 lat/lng, days, from, and station are already fully documented in the schema. The description reinforces the day-range and local-time semantics but adds no syntax or format detail beyond the structured fields — the baseline 3 for full schema coverage.

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 resource (high and low tide times) with the extra detail that heights and local-time framing are included. It reads clearly as the full tide-table tool, though it never names a sibling (e.g. best_low_tides) that an agent should consider instead.

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 only implied: the free/pass split tells the agent there are two access tiers but not when to prefer this tool over best_low_tides, currents, or water_temperature. No explicit when-to-use or when-not guidance is given.

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