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

With no annotations, the description carries the full burden and does well: it reveals the data source (787daily's validated reading of AAA's daily chart), availability start date, units, ordering, and inclusion of alert-band thresholds. It does not discuss error behavior or response structure, but those are secondary for a read-only history tool.

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 two sentences are information-dense and front-load the core purpose, then add source, scope, ordering, and usage guidance. Every clause contributes necessary context, though the long first sentence could be split for readability.

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 no output schema and no annotations, the description covers the essential facts an agent needs: what data is returned, source, units, scope, ordering, and intended use. Minor omissions like a full list of valid reservoir slugs are mitigated by the schema example and the 'omit for all' fallback.

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 already documents both parameters thoroughly, including defaults, constraints, and an example slug. The description adds only high-level scope ('one or all 19 reservoirs') and does not explain parameter syntax beyond the schema, so a baseline score 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 the tool's function: retrieving daily history of AAA reservoir levels, with units, scope (one or all 19), ordering, and alert-band thresholds. It does not explicitly name sibling alternatives, but the historical framing ('Daily history', 'trends, day-over-day change') distinguishes it from status-oriented tools like get_water_status.

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 explicitly states intended use cases: 'Use for trends, day-over-day change and band crossings.' It does not mention alternatives or exclusion criteria, but provides enough context for an agent to decide when this tool is appropriate.

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