list_contacts

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

With no annotations, the description must cover behavior. It does not explicitly state that the operation is read-only (no destructive hints), does not mention authentication requirements, rate limits, or what happens if the audience_id is invalid. The default limit of 20 is mentioned in the schema but not in the description.

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, efficient sentence. It is front-loaded with the key information. However, it could be slightly longer to add essential behavioral context without losing conciseness.

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 simplicity of the tool (2 params, no output schema, no annotations), the description is minimal. It lacks details about return format, error handling, sorting order, or whether pagination supports cursors. A listing tool should provide enough context for an agent to understand the response structure.

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%, so the schema already documents both parameters. The description adds no additional meaning beyond the schema's descriptions (e.g., audience_id is 'Audience ID (e.g. from your Resend dashboard)'). Baseline 3 is appropriate.

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 'List contacts in a Resend audience' clearly states the action (list) and resource (contacts) within a specific scope (in a Resend audience). It distinguishes well from sibling tools like create_contact (create vs list) and list_domains (different resource).

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?

No guidance is provided on when to use this tool vs alternatives, such as whether to use it for initial retrieval or if there are prerequisites like an existing audience. No mentions of filtering, sorting, or when not to use it (e.g., for large datasets where pagination might be needed).

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