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

Annotations already declare readOnlyHint=true and openWorldHint=true, so safety is covered. The description adds real context beyond them: dual currencies (EUR and DKK per MWh), the quarter-hourly vs hourly nature, the returned summary statistics (min/max/average, cheapest hours), and the publication timing. It does not cover error or edge behavior, keeping it short of a 5.

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 tightly written sentences that front-load the core purpose and append the timing caveat. Every clause carries information; nothing is 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?

With no output schema, the description partially carries the return-value burden by naming the currencies, units, resolution, and summary measures (min/max/average, cheapest hours). Combined with 100% parameter coverage and read-only annotations, an agent has enough to call it correctly, though the exact response shape is not spelled out.

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 all four parameters with defaults, enums, and patterns. The description restates the same concepts (one day, bidding area, hourly/quarter-hourly, cheapest hours) without adding syntax or format detail, so the baseline of 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 gives a specific verb and resource: 'Day-ahead electricity spot prices for one day and bidding area.' It also states units (EUR/DKK per MWh) and resolutions, making the resource fully identifiable and distinguishable from the nearest sibling (dk_co2_intensity), which covers a different Denmark energy datapoint.

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 provides clear usage context, notably the timing cue 'Tomorrow's prices are normally published around 13:00 CET,' which tells an agent when tomorrow's data is actually available. There is no explicit when-not-to-use or named alternative, but no confusable sibling exists, so context is adequate.

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