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

Annotations already declare readOnly, openWorld, idempotent, and non-destructive behavior. The description adds useful context beyond annotations: coverage of 518 water bodies from 1992 to present, satellite radar altimetry as the data source, and the return shape including latest reading, measuring satellite, history, and change over time.

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?

Three sentences with the core function front-loaded, followed by scope and use cases. Every sentence earns its place, and the examples of specific lakes are illustrative without being excessive.

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 simple read-only tool with two parameters and no output schema, the description explains data source, coverage, return contents, and use cases. It omits units and exact response formatting, but that is not critical for correct invocation.

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 description coverage is 100%, so the schema already documents both parameters. The description reinforces that 'lake' is a named water body and mentions 'recent history', but it does not add meaningful detail about the 'history' parameter beyond what the schema provides.

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 current and historical water levels for a named lake, sea, or reservoir, and specifies the data source and output. It does not explicitly distinguish itself from the sibling lake_level_search, but the 'named lake' framing and return details make the purpose clear.

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 gives explicit use cases: questions about rising or shrinking lakes, drought and reservoir storage, and inland water body levels. It does not mention alternatives or exclusions, but the context is clear enough for an agent to know when to invoke it.

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