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

Annotations already cover safety (readOnlyHint), idempotency, and non-destructiveness. The description adds valuable behavioral context by explaining the id semantics: ids count from 1, are safe to display, and are what other tools expect. This goes beyond the schema and 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 with no wasted words. The main action and scope are front-loaded, and the additional id semantics sentence earns its place by providing crucial cross-tool context.

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 optional parameter, full schema coverage, rich annotations, and an output schema, the description is complete. It additionally covers the non-obvious id convention that agents need for downstream tool calls.

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 sole parameter, status, is fully documented in the schema with its enum values and default behavior, so the description does not need to repeat it. The description adds no extra parameter-level meaning, but with 100% schema coverage the baseline of 3 is appropriate.

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 a specific action and resource: 'List registered waters for the account.' This is distinct from the sibling register_water and list_* tools by resource type, though it does not explicitly name a sibling to differentiate from.

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 makes it clear that this is the tool for listing registered waters, and the account scoping is stated. However, it does not provide explicit guidance on when to use this over list_recipes or other listing siblings, nor does it mention exclusions. Usage context is implied rather than explicit.

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