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

Annotations already declare readOnlyHint=true, so safety is covered; the description goes further by disclosing the default factor set (Cornerstone/AR6) versus edition=2025 (AR5) and that CO2e shifts slightly, plus that biomass CO2 is reported separately as biogenic. It does not discuss error handling or the 50-item cap, but the substantive behavioral caveats are present.

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?

Long but dense and front-loaded: purpose first, then defaults, then input format with examples, then scope exclusions, then return values and sibling pairing. Every sentence carries information, though the description sits at the upper end of acceptable length.

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 only a readOnlyHint annotation and no output schema, the description carries the burden well: it states the returned shape ('per-item and total CO2e'), the default and alternate editions, the biogenic reporting convention, and the boundary against vehicle-fuel and Scope 2 use cases.

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 50% (quantity is undocumented), so the description must add meaning, and it does: it maps fuel classes to plausible units ('natural gas in therms/ccf/mcf/scf, propane/diesel/heating oil in gallons, coal in short tons') and explains the edition switch's effect on CO2e. This exceeds the baseline for a half-documented schema, though it does not fully document the quantity parameter's bounds.

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 with precise scope: 'Calculate Scope 1 stationary-combustion emissions (CO2, CH4, N2O and CO2e) for fuels burned on site.' It names the factor source and explicitly confines itself to stationary sources, which distinguishes it from calculate_emissions (Scope 2 electricity) named in the same description.

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?

Explicit when-to-use ('fuels burned on site', 'stationary sources only'), when-not ('for vehicle fuel the CO2 per gallon is the same, but CH4/N2O factors differ and are not included'), and the alternative to pair with ('Pair with calculate_emissions for a facility's electricity (Scope 2)'). Routing is unambiguous.

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