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

Annotations already declare readOnlyHint and idempotentHint, covering the safety profile. The description adds useful context beyond annotations: the data source URL (environment.data.gov.uk/hydrology), the Open Government Licence, and the explicit 'no auth required' statement.

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?

A well-structured single paragraph: purpose, filters, return fields, next-step usage, and data source. Nothing redundant, though it could be slightly tighter by merging the licensing note with the data source.

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?

Given that the output schema is not provided but the description lists the return fields, and annotations cover read-only/idempotent, the description is complete for an agent to call correctly. Missing sorting/pagination details are minor since the limit parameter is described 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?

All four parameters have full descriptions in the input schema (100% coverage), so the baseline is 3. The description summarizes the filters (river name, freetext, measured property) but does not add meaning beyond what the schema already provides for each parameter.

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: search the UK Environment Agency hydrology monitoring network for stations. It enumerates filter types (river name, freetext, measured property) and return fields (station_id, name, river/catchment, coordinates, measure count), and distinguishes itself from siblings by explicitly pointing to ea-hydrology.station_measures for the next 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?

Explicitly tells the agent to use the returned station_id with ea-hydrology.station_measures to see available data series, which routes to the correct sibling. It also notes 'no auth required', setting clear expectations for when this tool can be invoked.

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