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

Annotations already cover read-only, idempotent, non-destructive, open-world traits, so the description is not carrying the safety burden. It adds genuinely new context by disclosing the pricing model (free within the daily allowance, then $0.001 USDC per call via x402), which an agent needs for cost-aware invocation, plus the day-2-to-14 data 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?

Two compact sentences with zero filler. The core purpose and data horizon are front-loaded, and the pricing caveat follows in second position where it belongs.

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 present, the description needn't document return values, and the annotations carry the safety profile. Purpose, horizon, and cost are all covered; the only missing piece is disambiguation from the similarly named surplus and indicated forecast tools.

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 no parameter semantics for the description to explain; baseline 4 applies. The stated days 2–14 range and OCNMFD2 code give useful framing for what the parameterless call will return.

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 ('daily operating margin forecast') and pins the horizon to days 2–14 with the upstream data code OCNMFD2. It is clear what the tool returns, though it never names or distinguishes itself from the closely related gb-electricity__surplus-forecast sibling, which an agent could easily confuse with 'margin'.

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 when-to-use, when-not, or alternative guidance is given. The description implies forecasting usage but does not say how this differs from surplus-forecast, demand-forecast-14d, or indicated-forecast, all of which are plausible siblings for a grid-balance question.

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