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

Annotations already declare readOnly, idempotent, openWorld and non-destructive, so safety is covered. The description adds genuinely non-obvious result-ordering behavior: primary measurements are returned ahead of their companions (standard deviation, value counts, flags), which affects how an agent should interpret the first hits. It does not mention empty-result behavior or that results may be truncated by limit.

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 short sentences, front-loaded with the core action, then the downstream purpose, then the ordering caveat. No filler and nothing redundant with the schema.

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 an output schema present, return values need not be explained, and the ordering note plus the estimate/get_data linkage covers the main agent needs for a 4-parameter search. Minor gap: no guidance on narrowing a too-broad query or on what an empty result implies.

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 75%, and the schema already documents the free-text query, store filter and domain values, so baseline is 3. The description restates the searchable axes (name, quantity, unit) but adds nothing about limit semantics or how store/domain constrain ranking – no compensation beyond schema.

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 and resource ('Find variable ids in the ICOS catalogue') plus the three search axes (name, quantity, unit). It further distinguishes itself from siblings by naming the consumers of its output ('The ids are what estimate and get_data take'), so an agent knows this is the discovery step, not a data-fetch step.

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 mention that ids are consumed by estimate and get_data clearly implies this is a prerequisite/discovery call before those tools. However, it never explicitly says when not to use it, e.g. that describe_variable should be used to inspect metadata for an id already known, or that list_datasets is better for browsing stores.

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