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

Annotations already declare readOnlyHint=true and idempotentHint=true, so the read-only nature is covered. The description adds value by specifying exactly what data is returned (current value, previous period, baseline, targets, on-track status), which goes beyond the annotations and helps the agent understand the output without an 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?

The description is a single, well-structured sentence that front-loads the action and resource, then lists the key data fields. No unnecessary words or repetition.

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 tool has only one parameter and annotations cover safety, the description provides a comprehensive list of what the response will contain (current value, previous period, baseline, targets, on-track status). This is sufficient for an agent to know what to expect, and no critical details are 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?

The schema fully describes site_id as 'The site id, as returned by list_sites', so the parameter semantics are already clear. The tool description does not add additional meaning beyond that, so a baseline score of 3 is appropriate given high schema coverage.

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 tool shows goals per metric for a website, listing specific data fields (current value, previous period, baseline, targets, on-track status). This differentiates it from siblings like get_site_metrics or get_report by focusing specifically on goals per metric.

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 implies the tool is for retrieving goal-related metrics, but does not explicitly mention alternatives or when not to use it. However, the clear resource scope (goals per metric) provides sufficient context to distinguish it from other reporting tools, though it lacks explicit exclusions.

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