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

Annotations already declare readOnlyHint, idempotentHint, openWorldHint, and non-destructive behavior, so the safety profile is covered. The description adds genuine value beyond annotations by defining the tier classification semantics (Tier I = established methodology, Tier II = methodology in development, Tier III = no agreed methodology), which an agent needs to interpret results correctly. It also clarifies the output contents (series codes, data series codes) beyond what annotations express.

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 with zero filler: the first covers core purpose and return contents, the second covers filtering behavior, and the third covers downstream usage with concrete examples. Each sentence earns its place, and the most decision-relevant information (what is listed) is front-loaded.

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 the low complexity (2 optional params, no required params), a rich output schema, and comprehensive annotations, the description covers what is needed: returned fields, tier semantics, filter options, and routing to unsdg.data.query. The only minor gap is that behavior when supplying target without goal is delegated to the schema's 'for best results' phrasing rather than clarified in the description itself.

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%, with goal and target both already documented including examples, ranges, default behavior (all 231 indicators), and the soft dependency of target on goal. Per calibration, this sets a baseline of 3. The description's 'Optionally filter by goal (1–17) or target (e.g. "3.3")' largely restates schema content, adding little new parameter meaning.

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 specific verb+resource: 'List UN SDG monitoring indicators with their series codes, tier classifications... and associated data series codes.' It names exactly what is returned and implicitly distinguishes itself from the sibling family — unsdg.data.query fetches time series data, while this tool catalogs indicators. The downstream reference to unsdg.data.query further disambiguates the resource boundary.

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 final sentence gives explicit routing guidance: series codes obtained here are 'the inputs to unsdg.data.query for fetching actual country-level time series data.' This tells the agent when to use the listing tool versus the data query tool. However, it does not explicitly contrast with the other sibling listing tools (unsdg.goals.list, unsdg.targets.list), leaving that differentiation to naming conventions and inference.

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