search_variables

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

Annotations already cover the safety profile (readOnly, idempotent, non-destructive, openWorld), so the bar is lower. The one genuine addition is the result-ordering trait: "Primary measurements come before their companions (standard deviation, value counts, flags)," which the agent cannot infer from the schema. Nothing is said about ranking, matching behaviour on partial terms, or empty results, and the return shape is covered by the output 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?

Three short sentences, purpose front-loaded, followed by the downstream use and then the ordering caveat. No filler or restatement of the tool name, and every sentence contributes information the agent would otherwise lack.

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?

The tool is a simple, well-annotated search with full schema coverage and an output schema, so return values need no explanation. Purpose, downstream use, and result ordering are all present; the only thin spot is interaction with the optional `store`/`domain` filters, which are already documented in 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 description coverage is 100%, including concrete examples for `text` and defaults/bounds for `limit`, so the schema carries the parameter burden. The description only restates the searchable facets (name, quantity, unit) without adding syntax, matching, or filter-combination semantics. 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 gives a specific verb and resource ("Find variable ids in the ICOS catalogue") plus the searchable dimensions (name, quantity, unit), so the agent knows exactly what the tool returns. It does not, however, contrast itself with the closely related sibling describe_variable, so the boundary between "search for an id" and "describe a variable" is left implicit.

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?

It states the downstream contract clearly — "The ids are what estimate and get_data take" — which tells the agent this is the lookup step before those tools. It stops short of explicit when-not guidance or naming alternatives such as describe_variable or find_stations.

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