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

Annotations already declare readOnlyHint=true and openWorldHint=false, so safety is covered. The description adds real value beyond that: data provenance (DESNZ QEP tables), freshness ('latest quarterly'), and the CCL inclusion/exclusion variants, which tells the agent what the numbers actually represent. It does not describe return shape or how far back the series goes.

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 dense sentences, front-loaded with the resource and scope; the caveat 'Statistics, not a quote' lands last for emphasis. Nothing is redundant and no sentence could be dropped without losing information.

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 one-optional-parameter, read-only statistical lookup with no output schema, the description covers subject, segmentation, variants, and provenance well. Minor gaps: no indication of the time series depth available or the shape of returned values, which an agent might want since no output schema exists.

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% and the single 'band' parameter is fully documented with an example and MWh range, so the schema does the heavy lifting. The description adds the framing that bands are annual-use size bands, but no matching syntax or accepted band list beyond the schema's example.

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?

Names a specific verb and resource (latest quarterly price per kWh paid by UK businesses), the segmentation (annual-use size band), the measurement variants (including/excluding Climate Change Levy), and the source (DESNZ QEP tables 3.4.1/3.4.2). The closing 'Statistics, not a quote' separates it from the sibling cost/quote tools such as charging_cost, commercial_solar_cost, and host_income_estimate.

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?

'Statistics, not a quote' gives a clear selection signal: use this for published official price data rather than for a personalised estimate. It stops short of naming an alternative sibling or stating exclusions, so it is clear context rather than explicit routing.

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