get_domain_performance

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

Discloses authentication method (API key), rate limits (max 10 concurrent requests), and idempotency ('Read-only, safe to retry'). Since no annotations are provided, the description fully covers behavioral traits.

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?

Well-structured with sections for Args, Returns, and an example. A bit lengthy but every sentence adds value. Could be slightly tighter.

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 one parameter and an output schema, the description provides a thorough explanation of the return format and behavior, making it complete for an agent to use correctly.

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?

Adds meaning beyond the input schema by describing the param as 'The Mailchimp campaign ID (e.g. 'abc123def4')' and specifying it 'Must be a sent campaign', which is critical context not present in the schema.

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?

Clearly states the verb 'Retrieve' and the resource 'campaign performance broken down by recipient email domain'. Distinguishes from sibling tool 'get_campaign_report' by specifying it provides domain-level breakdown, not aggregate metrics.

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 states when to use (identify deliverability issues, compare engagement across domains) and when not to (use get_campaign_report for overall metrics). Also specifies prerequisite: 'Only works for sent campaigns'.

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