Freight & logistics emissions (Scope 3 Cat 4 & 9), GLEC tonne-km method: emissions = tonnes × km × factor. Find mode factors via search_factors (section "freight" or "freight_detailed"), e.g. freight.road_hgv.tonne_km.
| Name | Required | Description | Default |
|---|---|---|---|
| mass | Yes | { "value": <number>, "unit": "tonne|kg|lb" }. | |
| distance | Yes | { "value": <number>, "unit": "km|mi|nmi" }. | |
| factor_key | Yes | Per-tonne-km freight factor key. |
Does the description disclose side effects, auth requirements, rate limits, or destructive behavior?
With no annotations, the description carries the transparency burden; it discloses the calculation method ('emissions = tonnes × km × factor') and the factor-key source. It doesn't cover error handling or output details, but the formula fully specifies the core behavior of a calculation tool.
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 sentences convey scope, method, formula, and factor lookup; no filler or repetition of schema fields.
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 3-parameter calculation tool with no output schema, the description provides the formula, factor lookup route, and example, which is sufficient for basic invocation. It leaves minor ambiguity about output format and invalid-factor behavior, but these are lower-stakes for a deterministic calculator.
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?
The input schema already documents all three parameters (100% coverage), but the description adds meaning by expressing the formula that connects mass and distance to the factor, and by giving a concrete factor_key example ('freight.road_hgv.tonne_km') plus a lookup path via search_factors.
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 specifically identifies the tool as calculating 'Freight & logistics emissions (Scope 3 Cat 4 & 9)' and gives the exact GLEC tonne-km formula, clearly distinguishing it from sibling calculate_* tools for other emission categories.
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?
It provides concrete usage context by stating the GLEC method and instructing users to 'Find mode factors via search_factors', with an example key. It doesn't explicitly say when not to use it or mention alternatives like calculate_activity, but the freight/logistics framing makes the intended scenario clear.
Agents often have multiple tools that could apply. Explicit usage guidance like "use X instead of Y when Z" prevents misuse.
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Each tool has a clearly distinct role: search, lookup single, lookup batch, resolution, absence explanation, and separate calculation methods for distinct scopes. Even the discovery tools can be told apart by whether the input is a key, text, natural language, or a purpose. Domain calculators are cleanly separated by type of activity, so an agent should not confuse them.
All tools follow a consistent verb_nonn pattern: calculate_*, lookup_factor(s), search_factors, resolve_factor, explain_absence. The naming clearly signals both action and object, and even the singular/plur lookup distinction matches the batch versus single-key semantic.
Twelve tools is well-sopened for a broad emissons-factor API: six calculators, four discovery/lookup/resolution tools, one batch lookup, and one edge-case explainer. Each tool appears to serve a necessary purpose rather than adding redundant surface area.
The set covers the full workflow: discover factors, resolve amiguous plain-language queries, look them up individually or in batch, perform domain-relevant calculations, and even explain why a factor is absent. The main GHG scopes are covered by dedicated calculators while the generic calculate_activity fills gaps for any other factor data.
