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

Annotations already declare readOnly/idempotent/openWorld=false, so the safety profile is covered; the description adds real behavior beyond that, disclosing that it routes each leg from coordinates or codes, that it may add legs ('legs Carbonara added'), and what the per-leg and step-by-step output contains. No contradiction with the read-only annotation since adding legs is internal to the calculation, not a persisted mutation.

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?

Three sentences, front-loaded with the purpose and standard, then routing behavior, then return shape. The return-value sentence is long but earns its place because there is no output schema.

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 correctly spells out what is returned (per-leg distance, method, data type, emission factor and source, DAF, added legs, and a step-by-step calculation sheet). It covers standards, routing and output adequately; only the when-to-use guidance 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 every parameter is already documented in the schema and the description need not carry that load. The description adds only a light touch ('Routes each leg's distance from its coordinates or codes'), so the baseline 3 is appropriate.

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 and resource ('Calculates one shipment's greenhouse gas emissions') and pins the scope with 'one shipment', implicitly separating it from the plural sibling calculate_shipments. It also names the standards (GLEC v3.2, ISO 14083), so the agent knows exactly what computation this is.

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 explains what the tool computes but never states when to choose it over calculate_shipments, get_methodology or emissions_report, and offers no exclusions or prerequisites. Usage is only implied by the singular scope and the emission-calculation purpose.

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