list_verified_domains

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

Annotations already indicate readOnlyHint=true, destructiveHint=false. The description adds practical behavioral context: authentication method (API key), max 10 concurrent requests, and safety to retry (read-only). This goes beyond annotations by specifying rate limits and retry safety.

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 concise with no redundant information. It is structured with a clear purpose statement, usage guidance, and separate Args/Returns sections that are easy to parse. Every sentence adds value.

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's simplicity (one optional parameter), the description covers all necessary aspects: purpose, usage, authentication, rate limits, and return structure. The output schema is implied by the Returns section, providing sufficient detail for an agent.

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 coverage is 0% for the 'account' parameter, but the description fully compensates by explaining its purpose (optional account name, naming convention, default behavior) and cross-referencing list_accounts. This provides clear guidance beyond the schema's type definition.

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 lists all sending domains verified for a Mailchimp account, with a specific verb 'list' and resource 'verified domains'. It distinguishes itself from the sibling tool get_verified_domain, which provides details for a single domain.

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 explains when to use the tool (to discover approved domains and check verification/authentication state) and directs to get_verified_domain for a single domain record. It also mentions authentication via API key and concurrency limits, but does not explicitly list scenarios where this tool should not be used.

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