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

Annotations declare readOnlyHint, openWorldHint, idempotentHint, and non-destructive, so the safety profile is already clear. The description adds meaningful behavioral context beyond annotations: it is a keyless public API, uses U.S. Government public-domain data, automatically chooses the nearest station for lat/lon, and returns water level relative to a datum with observation time in local station time and sample standard deviation when reported. It doesn't disclose all edge cases (e.g., what happens if no station is found), but it goes beyond 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 sentences front-loaded with the main purpose, then key usage alternatives and return details. Every clause earns its place without redundancy.

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 read-only, idempotent tool with all parameters documented in schema and a rich description of what it returns, it is largely complete. The only gap is lack of explicit behavior on errors or missing station, and no explicit mention of output format, but since there's no output schema and the tool is straightforward, the description covers what an agent needs to decide and invoke correctly.

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 the schema already documents all 5 parameters. The description adds useful context about the relationship between station and lat/lon ('nearest station is chosen automatically') and that datum defaults to MLLW, which is already in the schema. Baseline 3 is right because the description adds marginal context but doesn't need to compensate for schema gaps.

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 clearly states the tool returns the latest observed water level from a NOAA station, specifies the data source, keyless public API, how to identify a station (station id or lat/lon), and what the return includes. This is a specific verb+resource with clear scope, distinct from the sibling 'tide_predictions' (predictions vs observed).

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?

The description clearly indicates when to use it ('check current real-world water level versus prediction') and gives context about the data source. However, it does not explicitly identify alternatives or say when not to use it. Given the sibling list contains 'tide_predictions' which is a natural alternative, the description does not explicitly exclude or route to it, so a 4 is appropriate rather than 5.

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