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

Annotations already declare readOnlyHint, openWorldHint, idempotentHint, and destructiveHint=false, so the safety profile is covered. The description adds useful context beyond annotations: it notes no auth is required, identifies the upstream data source and license, and describes the response as containing each measure_id with its most recent date/time and value. No contradictions with annotations.

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 sentences, each earning its place: the first states the core function, the second summarizes the return value, and the third gives source/license/auth context. The description is front-loaded with the action and avoids unnecessary words.

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 simple (one parameter), and the description covers the essential points: what it returns, the source data, licensing, and authentication. An output schema exists, so detailed return fields are already structured. Nothing an agent needs to select or invoke the tool correctly is missing.

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%, so the parameter semantics are fully documented in the schema. The description reinforces that station_id comes from uk-ea-flood-monitoring.station_search, but this is also stated in the schema's parameter description. No additional semantic meaning beyond the schema is provided, so the baseline of 3 is appropriate.

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 clearly states the action: 'Get the latest reading for every measure... recorded at one UK Environment Agency monitoring station' and specifies the resource. It names the required identifier source (station_id from uk-ea-flood-monitoring.station_search) and the return shape (each measure_id with most recent date/time and value), making it unambiguous and distinct from sibling tools.

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 description gives clear context for use: it is the tool to call once you have a station_id from station_search, and it positions station_search as the prerequisite. It does not explicitly state when not to use it or name alternatives, but the context is strong enough for an agent to route correctly.

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