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

Annotations already declare read-only, idempotent, non-destructive, open-world behavior. The description adds a genuinely useful trait not in annotations: it is free within a daily allowance and then costs $0.002 USDC per call via x402, which an agent needs for budget decisions. No return-format or refresh-cadence detail, but the output schema covers returns.

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, zero filler. The core capability is front-loaded and the pricing caveat follows it.

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?

With an output schema handling return values, rich annotations, and an empty input schema, the description only needs to convey purpose and cost, which it does. The missing piece is routing guidance against the crowded sibling set of forecasts.

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 tool takes zero parameters, so there is nothing for the description to disambiguate; the baseline for a no-param tool is 4.

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?

States a specific verb, resource, granularity and horizon: 'Forecast available generation capacity by fuel type for the next two weeks.' That distinguishes it from demand-forecast, wind-forecast and generation-now siblings. It does not explicitly contrast itself with adjacent forecast tools (margin-forecast, surplus-forecast), so it stops short of a 5.

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?

No statement of when to use this tool versus the many other gb-electricity forecasts (demand-forecast-14d, margin-forecast, surplus-forecast, wind-forecast). The only secondary sentence is about pricing, not selection context.

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