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

With no annotations the description carries the full burden, and it does disclose substantive behavior: coverage of all six Annex I sectors, credit for carbon price already paid in the origin country, and pricing the same basket across years for trajectory visibility. It does not state determinism, idempotency, or failure modes for invalid sectors, so it falls short of 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?

Front-loaded with the core action and regulation, then splits scope and rationale. The middle sentence is a dense run-on bundling three capabilities, which slightly reduces scannability, but there is essentially no filler text.

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 deterministic computation tool with a fully documented schema and no output schema, the description covers inputs, domain scope, and the uncertainty it removes. It leaves open the shape of the returned cost breakdown, but nothing required to invoke it correctly is missing.

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 year, sector enum, and the certificate price requirement. The description adds mild meaning by tying origin_carbon_price_eur_per_tonne to a paid-in-origin credit and framing certificate_price as market-tracking, but does not deepen syntax or units beyond the schema. Baseline 3.

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 ('Compute') and a precisely-scoped resource (CBAM certificate cost of importing goods into the EU), anchored to named regulations and a year range. It is unmistakably distinct from the unrelated siblings eu_ai_act_classify and uae_corporate_tax.

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?

Explicitly directs use ('Use this rather than estimating') and explains why ('the phase-in factor changes every year and is the figure most often wrong'). It does not name a specific alternative tool or state exclusions, but the sibling set is unrelated, so this is strong contextual guidance.

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