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

Annotations already declare readOnlyHint=true, openWorldHint=true, and destructiveHint=false. The description adds useful context beyond them: the forecast horizon (7 days), the return unit (estimated kWh), and that the figure is weather-derived production rather than revenue. It does not describe fallback behaviour or accuracy/error characteristics, which are left to the schema.

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?

One dense sentence preceded by the endpoint, front-loaded with the core purpose and units. The 'GET /api/v1/solar-forecast' prefix is mildly redundant with the tool name but the rest is waste-free.

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 two-optional-parameter read-only tool with no output schema, the description supplies the essentials: what is returned, over what horizon, in what unit, and what sibling covers the adjacent profit use case. Only the geography constraint (US-only) and empty-argument fallback behaviour are absent, and the latter is covered by the schema.

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% and both parameters already carry descriptions including the fallback logic. The description's 'US ZIP + capacityW, 10000=10 kW' restates the schema rather than adding new meaning, so the baseline of 3 applies.

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 concrete verb ('GET'), resource ('/api/v1/solar-forecast'), and output shape (7-day estimated kWh from a home/small-business solar array). It also demarcates itself from the profitability/miner siblings, so the agent can distinguish it without reading another schema.

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?

Explicitly scopes the tool to weather-based production and tells the agent to use calculate_profitability or list_miners when the actual goal is miner profit. That is a real routing rule, though there is no explicit statement of when not to call it (e.g. non-US locations).

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