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

The description adds substantial behavioral context beyond the read-only annotation: the archive is populated three times a day, the series is daily-averaged, the archive starts on 2026-08-27, and callers should check seriesStartsAt because early windows are short. This discloses data limitations and response expectations that annotations alone do not convey.

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?

The description is compact and front-loaded with the core definition, followed by rationale and an operational caution. Each sentence earns its place with no filler or repetition of schema content.

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 tool with no output schema, it usefully reveals the response contains seriesStartsAt and that returned windows can be short. It could go further by describing the shape of the observations themselves, but the essentials for invoking and interpreting the archive are present.

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 key, days, and kind thoroughly. The description itself adds only contextual value about daily averaging and archive start date, not new parameter-level meaning.

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 clearly identifies the resource as a daily-averaged historical carbon price series and marks it as unique because it cannot be re-derived or obtained elsewhere. It lacks an explicit imperative verb in prose, but the tool name plus the noun-phrase makes the action unambiguous and distinguishes it from the current-price sibling tools.

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?

The description implies when to use it – whenever a historical carbon price series is needed, since no upstream API provides one. However, it does not explicitly state when not to use it or name an alternative such as get_carbon_prices for current prices.

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