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 two genuinely useful behavioral facts beyond that: prices are 'settled' (finalised, not estimates) and the data is gated behind a Pro tier. It says nothing about rate limits, availability windows, or what a missing market/region combination does.

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?

A single front-loaded sentence with zero filler: the resource, the time scope, the tier requirement and the aggregation option all appear before any padding. Nothing could be removed 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 5-parameter read tool with no output schema, the description is adequate but thin: it never sketches the returned shape (timestamped series?), says nothing about how the 7-day limit interacts with from/to, and does not clarify whether market/region pairs must match. It leans entirely on the schema's per-field descriptions to fill those gaps.

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 documented in the schema itself, which sets the baseline at 3. The description adds only marginal meaning, clarifying that 30m/60m intervals mean the data is averaged rather than sampled, and that the default window is the last 7 days.

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+resource: 'settled prices' over a defined historical window, with optional per-interval averaging. That clearly distinguishes it from forecast/day-ahead style tools by the word 'settled', though no sibling (grid_price, grid_day_ahead) is named explicitly, so the agent must infer which one is the live/forecast counterpart.

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?

There is no explicit when-to-use versus when-not guidance and no named alternative. The '(Pro)' marker hints at a plan prerequisite, but nothing tells an agent whether to reach for this tool or grid_price/grid_day_ahead when it wants prices.

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