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

Annotations cover safety (readOnlyHint, openWorldHint) and the description adds real behavioral context beyond them: an entitlement prerequisite (historical-data subscription) and a metering caveat (quota can count multiple requests for the range). These are exactly the failure modes an agent needs warned about before calling. It stops short of saying what happens if the range exceeds 31 days.

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 short sentences, front-loaded with the core operation and its hard limit before the quota and entitlement caveats. No filler or restated title.

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?

No output schema, but all parameters are documented at full coverage and the description supplies range limits, entitlement, and quota behavior for a non-destructive read. Only the error/behavior when the 31-day or subscription constraint is violated is left unstated.

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%, so all five parameters are self-documenting, including the enum for units and the exclusive-end_date rule. The description's restatement of the 31-day and exclusive-end constraints duplicating the schema means it adds no new parameter-level meaning; baseline 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 specific verb (read) and a specific resource (daily historical weather) with a scope constraint (at most 31 days). The word 'historical' implicitly separates it from the forecast siblings, but no sibling is named, so an agent must infer the routing.

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?

Gives hard constraints (31-day cap, end date exclusive, subscription requirement) so the agent knows when the call is valid, but never says when to prefer this over weatherbit_agriculture_history or weatherbit_energy_history, which likely return overlapping daily history for their domains. Usage is implied rather than routed.

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