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

Annotations already declare readOnly, idempotent, and closed-world, so the safety profile is covered. The description adds useful substance by naming the content categories returned (seasonality, hazards, ramps/marinas, playbooks), but says nothing about result shape, whether a passed slug that doesn't exist errors or returns empty, or how large the list response is.

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, zero padding, with the mode-switching rule placed last where it is easy to act on. The example slug is embedded rather than given its own sentence, which keeps it tight.

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 single-parameter, read-only lookup with no output schema, the description covers the essential question of what the agent gets back and how to get the overview list. The only missing piece is failure behavior for an invalid slug, which is minor at this complexity.

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 baseline is 3, but the description goes beyond the schema's bare "Waterway slug": it shows the slug format via an example (piscataqua-seacoast) and explains the meaning of omitting the optional parameter entirely, which the schema does not state.

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 gives a specific resource (waterways) and enumerates the content returned: seasonality, hazards, ramps/marinas context, playbooks. It even includes a concrete example slug, so an agent knows what the tool resolves. It stops short of a clean verb-first statement ("Focus waterways" is loose), but no sibling tool overlaps, so differentiation isn't needed.

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?

"Omit slug for the list" is a genuine usage rule that tells the agent how to switch modes, which is real guidance. Beyond that there is nothing about when this tool is the right choice versus get_state_boating_rules or get_safety_checklists, both of which touch adjacent regulatory/safety content.

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