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 discloses the data source (EIA-930, ~7-day window), the time basis (local time), and the shape of what comes back (cleanest and dirtiest windows, % saved vs daily average, all hours ranked). It omits operational traits such as auth requirements, rate limits, or staleness/data-latency beyond the 7-day window.

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 tight sentences with the core purpose front-loaded, the data basis and timezone next, and the most important caveat ('not a forecast') closing. No filler sentences and nothing redundant.

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 3-optional-parameter tool with no output schema and no annotations, the description supplies everything an agent needs: what is computed, from what data, on what time basis, and what the response contains. Return-value explanation is present because no output schema exists to carry it.

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 ba, zip, and duration (including the default of 4). The description reinforces the 'N hours' window semantics and the ZIP-or-BA granularity, but adds little beyond what the structured fields state, so the baseline 3 applies.

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 opens with a specific verb and resource: 'Find the cleanest (lowest grid carbon) contiguous window of N hours in the day to run a flexible load'. It explicitly scopes itself against siblings like hourly_intensity by clarifying it is a historical scheduling guide, not a forecast, so an agent can route without opening any schema.

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?

It gives concrete use cases (batch jobs, EV charging, pumping, HVAC pre-cooling) and a clear data basis (hour-of-day pattern of the last ~7 days of EIA-930, local time), plus the crucial 'guide from recent history, not a forecast' caveat. It stops short of naming which sibling to use instead when a forecast is wanted, so no explicit alternative is provided.

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