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

With no annotations, the description carries the full behavioral burden and does substantive work: it discloses the 31-day maximum range, that times are in local time, and that output includes daily min/max/mean plus cheapest/priciest N-hour windows. It does not state units/currency, data freshness, or whether future days beyond day-ahead are available, which keeps it below 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 packed sentences: the first front-loads what the tool returns and its constraints, the second covers when to use it. No filler and nothing 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?

An output schema exists, so return values need not be spelled out, and the description covers purpose, constraints, and usage triggers adequately for a 4-parameter read tool. The remaining gap is peripheral detail such as price units/currency and accepted date formats.

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 0%, so the description must compensate, and it largely does: the zone examples effectively enumerate valid zone values, 'up to 31 days in local time' bounds the start/end parameters, and 'cheapest and priciest N-hour window' explains window_hours. It omits date string format and the null/default behavior of start and end, so not a full 5.

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 states a precise verb+resource ('Day-ahead wholesale electricity prices') and scopes it to a European bidding zone, even listing example zone codes (DE-LU, FR, NL, AT, BE, PL). An agent can immediately distinguish this from unrelated siblings like evm_gas_fees or us_company_filings.

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 gives concrete triggering scenarios: 'Use when scheduling EV charging, heat pumps or batteries, or asked what power costs tomorrow.' That is clear when-to-use guidance. It stops short of explicit when-not-to-use or naming an alternative sibling (e.g., bess_arbitrage_revenue), so it is a 4 rather than a 5.

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