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

The readOnlyHint annotation already covers the read-only nature. The description adds 'cursor page' and API reference, disclosing pagination behavior. However, it does not detail response format or rate limits, but with annotation coverage the bar is lower, matching the 3-level where added value exists without being comprehensive.

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, front-loaded sentence that communicates the primary action and scope, with no redundant details. Every word earns its place.

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 simple list operation with good annotations and full schema coverage, the description sufficiently covers core behavior. The mention of 'cursor page' aligns with pagination params, and the tool name implies the return of contacts. Although no output schema exists, the description is adequate for this low-complexity tool.

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 input schema provides full descriptions (100% coverage) for all three parameters, including limit, audience_id, and starting_after. The description's 'cursor page' phrasing hints at pagination but does not add meaning beyond what the schema already documents, so 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 clearly states the action ('List') and the resource ('contacts that belong to a static audience'), distinguishing it from sibling tools like list_contacts which likely lists all contacts. Including the API endpoint reinforces the specific scope.

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 clear context by specifying 'a static audience', implying this tool is for audience-scoped contact retrieval. It does not explicitly mention alternatives or exclusions, but the context is sufficiently distinct.

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