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

Annotations already declare readOnlyHint, idempotentHint, and non-destructive behavior, so the safety profile is covered. The description adds substantive domain context beyond that: the unit conventions by material class, the A-D gradation, and virgin vs PEF CFF variants, which help the agent anticipate the shape of the data.

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?

Front-loaded with 'Carbon footprint' and kept to one dense sentence plus a short application note; nothing is padded. It leans heavily on domain jargon (L3, CFF, cullet) but the length is appropriate.

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 carries the burden of describing return values and largely does — units, grades, and material classes are spelled out, and annotations cover the safety profile for a 2-parameter lookup. The main gap is the absence of routing guidance against the other index tools.

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 both parameters are already documented. The description echoes the recycled-content optionality and adds the surrounding context (virgin and PEF CFF), but no syntax or format detail beyond what the schema provides — 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 specifies the resource precisely (carbon footprint factors for finished packs and raw materials) and the conventions used (kg CO2e per unit vs per tonne, grade A-D). It never states the retrieval verb explicitly, but the domain content is specific enough to distinguish it from the price/forecast siblings.

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?

'For Scope 3 Category 1: factor × units or tonnes' gives context for how the returned value is applied, which is useful. However, it never says when to pick this tool over get_live_index, get_index_history, or get_all_indices, so tool selection is left to inference.

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