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

Annotations already declare readOnlyHint and openWorldHint, but the description goes well beyond them: it discloses the data source (NOAA CO-OPS, US public domain), coverage limits, the 404-not-charged behavior, the exact price and payment rails (x402 on Base, Solana, Arc), and that failed calls are not charged. This is unusually rich behavioral context for a read-only API 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 description is dense and front-loaded, starting with what the tool returns and following with inputs, coverage, and pricing. It is slightly redundant — 'not charged' appears twice — but every sentence otherwise earns its place.

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 an output schema present and annotations covering safety/open-world status, the description still supplies the missing operational context: geographic coverage, failure semantics, and payment mechanics. Nothing material is left for the agent to infer.

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 description coverage is 100%, so the schema already documents all six parameters, and the description mostly restates their roles (lat/lon together, place as alternative, search lists stations instead of predictions). It adds no syntax or format detail beyond the schema, matching the baseline of 3 when structured fields carry the load.

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 output (tide predictions: high and low water, metres above MLLW, UTC times) and a precise scope (1–7 days at the nearest NOAA station or a station id). It clearly distinguishes itself from weather/sun and other environmental siblings without ambiguity.

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 states concrete input paths (give lat and lon, a place name, or a station id) and usage constraints (US coverage only; points >100 km from a station return 404). No alternative sibling tool is named, but the when-to-use conditions and failure cases are clear.

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