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

Annotations already declare readOnly/idempotent/non-destructive, and the description adds genuinely new behavioral facts: the ~0.25 degC validation accuracy against published tables, the 90% tested range for Enhanced, the 1-credit cost of the DDY file via web or API, and that the two modes are never mixed. Cost and accuracy disclosures are exactly the kind of context annotations cannot carry.

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?

Front-loaded with the one-line summary, then a per-mode block, so an agent can read only as far as it needs. A few phrases are slightly redundant ('not the ASHRAE method', 'that are never mixed') but the density of useful facts per sentence is high.

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?

An output schema exists, so return values need not be described, and the two modes plus cost are well covered. The gaps are the undocumented current_climate flag and location_name, plus no note on units or how the result differs from get_nearest_stations output for the same coordinates.

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?

With 0% schema description coverage the description must carry the load, and it does for the two most consequential parameters: mode is explained in depth for both values, and the full edition list (2025, 2021, 2017, 2013, 2009, 2005) is supplied even though the schema declares no enum. However, location_name and current_climate receive no explanation at all, leaving two of six parameters undocumented anywhere.

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 resource (heating and cooling design conditions for a site) and the two distinct computation modes, which no sibling (analyze_epw, generate_tmy, get_nearest_stations) offers. An agent can immediately tell this is the design-condition lookup rather than an EPW analysis or generation tool.

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?

Explains what each mode means — ASHRAE Ch. 14 replicated at the nearest station for a chosen edition versus EPW.tools Enhanced computed at the site for today's climate — which lets an agent pick a mode from the requirement. It stops short of an explicit 'use mode X when you need Y' statement and never mentions when to prefer siblings like get_nearest_stations or analyze_epw.

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