list_contacts

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

Annotations already declare readOnlyHint=true, idempotentHint=true, and destructiveHint=false, so the safety profile is known. The description adds that the tool returns subscription status and engagement metrics, and it mentions filtering by status. It does not describe pagination behavior, rate limits, or response format, but with annotations covering the read-only nature, the added context is adequate but not rich.

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 exactly two sentences: the first states the core action and scope, and the second gives a concrete use case. There is no redundant information, and the most important information 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?

This is a low-complexity listing tool with four optional parameters and no output schema. The description covers the main functionality and a specific use case. It could be slightly more explicit about what engagement metrics are returned, but for a list operation with good schema coverage and read-only annotations, it is sufficiently complete.

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 all four parameters (page, limit, search, status) already documented. The description reinforces the purpose of the status filter by mentioning 'unsubscribed or bounced' but does not add substantial meaning beyond the schema. The schema already describes each parameter sufficiently, so the description adds only marginal value.

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 starts with 'List contacts'—a specific verb and resource—and further specifies that it returns subscription status and engagement metrics. This clearly differentiates it from sibling tools like create_contact, update_contact, import_contacts, and get_contact_score, which involve different operations on contacts.

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 provides concrete usage context: 'Filter by status to find unsubscribed or bounced addresses that should be excluded from sends.' This tells the agent when to use the tool and the purpose of the status filter. However, it does not explicitly state when not to use it or mention alternatives for other contact-related tasks, so it falls short of a 5.

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