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

Annotations already declare readOnlyHint, idempotentHint, openWorldHint and destructiveHint=false, so the safety profile is covered. The description adds genuinely non-structured behavior: nearest-first ordering and the billing model (free within the daily allowance, then $0.001 USDC per call via x402), which the agent cannot learn from annotations.

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 dense sentences with no filler: the geographic scope and default radius come first, then the ordering and cost. Every clause carries information an agent needs.

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, return values need no explanation, and annotations cover the safety profile. The description adds the ordering and pricing context that structured fields lack; only the precise mechanics of the 'daily allowance' remain unstated, which is a minor gap.

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 lat, lng, limit and radius_km are already documented, and the description only restates the 50 km default that the schema already gives. The one addition beyond the schema is result ordering ('nearest first'), which is useful but minimal. Baseline 3 applies.

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 and resource: NOAA tide-prediction stations within a radius of a point, returned nearest-first. An agent can distinguish it from tides__station (single station) and tides__search, though it never names a sibling explicitly.

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 by the phrasing 'stations near a point,' which tells the agent this is the proximity lookup, and the pricing note hints at when cost applies. However, there is no explicit when-to-use/when-not guidance or routing to tides__station or tides__search for other cases.

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