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

Annotations already indicate read-only, idempotent, and closed-world behavior. The description adds that the catalog is 'static, built-in,' which further clarifies that no external calls or mutations occur. While it doesn't mention error cases or rate limits, the bar is lower given annotations, and the added context is meaningful.

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 two sentences, front-loaded with the main purpose, then providing concrete examples and usage. It is concise, well-organized, and avoids unnecessary fluff.

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?

Given the simple nature of the tool and the richness of the schema, the description is complete. It covers what the tool returns (codes, names, units, domain), gives usage guidance, and provides examples. No critical information is missing for an agent to use it 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?

The input schema fully describes the 'group' parameter with an enum and default, including a detailed description. The tool description merely repeats the filter concept ('Filter by group') without adding new semantics. Since schema coverage is 100%, the baseline is 3, and the description does not exceed it.

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's function: listing USGS parameter codes with human-readable names, units, and thematic domain. It distinguishes itself from sibling tools (dataframe operations, site/conditions/readings/series) by focusing on the code catalog, and even provides concrete examples (00060 = 'Discharge' ft³/s).

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?

Explicit usage guidance is provided: 'Use this first to discover...' and 'Filter by group to narrow results.' This tells the agent when to invoke this tool (before data retrieval) and how to use the filter, which is sufficient given the sibling tools context.

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