EU Electricity Prices API: Day-Ahead Power Prices & Cheap Hours

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

Annotations already declare readOnly and openWorld, so the safety profile is covered. The description adds real behavioral value beyond that: the pay-per-result cost model ($0.003 start, $0.0002 per row) and the fact that tomorrow's data is published around 13:00 CET — both actionable expectations.

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?

Dense and front-loaded: resource and scope first, then defaults, then pricing. Every sentence earns its place, though the pricing sentence is somewhat tangential to invocation.

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 steps in to describe the returned shape (per-zone/day summary with cheapest window, min, max, average, negative-price hours), covering what an agent needs to interpret results.

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 coverage is 100%, so all five parameters are already documented in the schema, including defaults and semantics. The description's mention of summary fields and negative-price hours adds context but no parameter-level syntax beyond the schema, so the baseline 3 is appropriate.

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 ('Day-ahead electricity prices') with scope (40+ European bidding zones, hourly or 15-minute) and output content. An agent can immediately tell what this tool returns and no sibling covers the same ground.

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?

Gives concrete usage context: omitting dates returns today and tomorrow, with the publication timing noted. It doesn't state exclusions or point at alternatives, but the tool's niche is unique among its siblings so no routing guidance is needed.

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