List NHDPlus HR Service Layers

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

Annotations already declare readOnlyHint=true, idempotentHint=true, and destructiveHint=false, covering the safety profile. The description adds useful behavioral context by specifying the return structure (layers array with id/name/geometry_type and provenance) and error response format, which goes beyond the 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?

The description is compact and well-organized: it opens with a one-line purpose, then provides a 'Use when' section, a Returns JSON example, and an error response format. Every sentence serves a clear function with no 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 no-parameter listing tool with an output schema and strong annotations, the description fully covers the tool's behavior, output shape, and error handling. It also contextualizes its role among the find_* siblings, leaving no relevant gaps.

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?

The tool has zero parameters, so the schema coverage is 100% and the description carries no parameter burden. Per the rubric, a 0-param tool receives a baseline of 4, and no additional parameter explanation is needed.

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 states 'List the layers available in the NHDPlus HR service (id, name, geometry type)' which clearly identifies the verb (list), the resource (NHDPlus HR service layers), and the specific output fields. It also differentiates from the find_* sibling tools by noting it covers layers 'beyond those wrapped by the find_* tools.'

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 'Use when' section explicitly states two scenarios: discovering available layers beyond the wrapped find_* tools, and confirming current layer IDs. It also names the find_* tools as alternatives for feature-specific queries, providing clear context for when to prefer this tool.

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