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

Annotations already declare readOnlyHint=true and openWorldHint=false, so the safety profile is covered. The description goes further by disclosing the exact computation: base BTU from the ENERGY STAR area chart plus named adjustment factors (−10% shaded, +10% sunny, +600 BTU/person over 2, +4,000 BTU kitchen). It does not state the return format, but the arithmetic is fully transparent.

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: the first states the purpose and source chart, the second front-loads the formula and its adjustments. No filler, and the most decision-relevant information (what it computes and how) leads.

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 no-output-schema calculator with four optional, fully documented parameters, the description supplies the method and all adjustment rules, which is nearly everything an agent needs. The only minor gap is that the returned value (a BTU figure) is not explicitly described, though it is strongly implied.

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 baseline is 3, but the description adds meaning beyond the schema by tying each input to its numeric effect: shade maps to the ±10% adjustment, kitchen to +4,000 BTU, and occupants to +600 BTU each above two. This makes the parameters' impact on the result explicit rather than merely naming them.

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 states a specific verb+resource: it computes room air-conditioner capacity in BTU using the ENERGY STAR sizing chart. The scope is unmistakable and clearly distinct from the other calc_* siblings (slab, paint, roofing, etc.), which compute unrelated quantities.

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?

Usage is implied by the name and the stated ENERGY STAR basis, so an agent can infer this is the tool for AC sizing. However, there is no explicit when-to-use guidance, no mention of when another tool (e.g. calc_appliance_energy_cost or calc_solar_panel) would be more appropriate, and no note on input expectations.

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