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

Annotations already declare readOnly, idempotent, non-destructive and closed-world behavior, so the safety profile is covered. The description adds genuinely useful domain context beyond that: the result is explicitly 'indicative', it discloses the regulatory basis (Reg 2025/2620 benchmark, CBAM factor 97.5% in 2026, CSCF) and that it shows the saving when actual data is supplied.

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 dense sentences, front-loaded with the cost scope before the formula detail. No filler, though the parenthetical formula stack is heavy enough to require careful parsing.

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 8 parameters (2 required) and no output schema, the description still covers the formula, the optional-input defaults and the indicative nature of the result, which is what an agent needs to call it correctly. Return-value shape is the only thing not described, and the 'Shows the saving with actual data' line signals the output direction.

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 baseline is 3 even without parameter prose. The description goes further by explaining how the key optional inputs interact with the calculation — default-value mark-up versus the producer's verified actual SEE, and the latest official quarterly price unless a price is provided — giving semantics the bare schema strings do not.

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 (estimate) and resource (CBAM certificate cost) and spells out the exact computation the tool performs: embedded emissions minus free-allocation adjustment, times certificate price. This is clearly distinguishable from siblings such as cbam_default_value, cbam_scope_check and get_pricing.

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 implicitly frames usage through its defaults ('default value with mark-up, or the producer's actual SEE', 'latest quarterly price unless given'), which tells the agent when to supply actual_see or certificate_price_eur. However, it never states when to use this tool versus siblings like cbam_default_value or get_pricing, nor any prerequisites or exclusions.

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