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

With no annotations provided, the description carries the full burden of behavioral disclosure. It merely states 'calculate' without revealing any operational behavior such as the use of default emission factors, the meaning of the returned value (e.g., total CO2e in kg), or that country defaults to GB. The schema hints at parameters but the description adds no behavioral context beyond the calculation intent.

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?

The description is a single, concise sentence that front-loads the primary action and includes helpful examples. Every word serves a purpose and there is no redundant information.

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?

The tool has four parameters and no output schema, yet the description provides no context about the return value (e.g., units, format), default behaviors (year, country), or how to ensure valid activity_type values. The minimal description is insufficient for a new agent to fully understand the tool's behavior beyond the schema, especially without annotations or sibling usage differentiation.

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% with each parameter described, so the baseline is 3. The description adds minimal value by listing example activity types (electricity, fuel combustion, materials, transport) which partially maps to the activity_type parameter, but it does not explain formats, units, or relationships between parameters beyond the schema.

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 clearly states the tool calculates CO2e emissions for an activity, using a specific verb and resource with examples of activity types. It distinguishes from some siblings (flight, freight, transaction) via the parenthetical list, but does not explicitly mention that it handles single activities only, making a slight distinction gap with calculate_emissions_activity_batch.

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?

There is no guidance on when to use this tool versus alternatives. The description does not mention that this handles a single activity while calculate_emissions_activity_batch handles multiple, nor does it contrast with flight/freight/transaction tools. The caller must infer usage from the name and sibling list, which is not explicit.

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