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

Annotations already declare read-only, idempotent, closed-world behavior, so the bar is lowered. The description adds genuinely useful substance beyond them: the data is double-averaged monthly (not raw), each month carries a zone, and availability windows differ (DSI since 2006, others since 1990), which tells the agent why early requests may return nothing.

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, front-loaded with the output definition followed by the use case, with no filler. The parenthetical availability note is dense but earns its place.

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 no output schema, the description does the work of describing the return shape (monthly averages plus a zone per month), which is what an agent needs. Only minor gaps remain, such as whether the range is inclusive or how large a response can get.

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 every parameter, including the enum meanings and YYYY-MM defaults, is documented in the schema itself. The description only restates the two-month range without adding format or constraint detail, so the 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?

The description states a concrete resource (monthly averages of one Isoba instrument) and the retrieval range (between two months), with useful coverage caveats per instrument. It implicitly separates itself from get_current_readings by returning historical averages rather than current values, but never names a sibling explicitly.

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?

"Use it for trends and to see what the instrument showed around past events" gives positive usage context but no exclusions or alternatives. An agent is left to infer that get_current_readings is for the present and get_track_record for something else.

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