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

Annotations already cover safety traits (read-only, idempotent, non-destructive), so the bar for extra behavior disclosure is lower. The description adds useful behavioral context: per-day row output, a configurable window, and the NOAA standard behind the default base temperature.

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?

Three tight, front-loaded sentences; the core metric appears first, followed by use cases and a domain-standard default. Every sentence earns its place with no filler.

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 zero required parameters and no output schema, the agent is left guessing whether it must supply lat/lon, zip_code, or both. The description also doesn't clarify what 'window' maps to in parameters, making correct invocation less certain.

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 only 20%, so the description needed to clarify lat/lon/zip_code and days_back semantics. It only indirectly references a window and the default base temperature, leaving location-parameter selection and window meaning mostly undocumented.

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 identifies the resource as heating and cooling degree days over a time window and specifies per-day row output. It is distinct from weather siblings like weather_current or weather_historical, though it doesn't explicitly name an alternative.

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?

The listed use cases ('HVAC sizing, utility bill reconciliation, energy forecasting') imply when the tool is appropriate, but there is no explicit guidance on when not to use it or which sibling to choose. The context is helpful but stops short of actual routing guidance.

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